Doctor of Philosophy (PhD), Wright State University, 2007, Biomedical Sciences PhD

Under normal conditions, blood pressure is tightly regulated through autonomic tonic and reflex mechanisms. However, when the set-point for blood pressure is chronically elevated, hypertension occurs. Hypertension if untreated can lead to further complications including heart failure, stroke and kidney failure. Elevated sympathetic outflow is known to contribute to the development and/or maintenance of hypertension, and while the hypothalamic paraventricular nucleus (PVN), a preautonomic center, has been implicated in the elevation of sympathetic activity during hypertension, the precise pathophysiological mechanisms underlying sympathoexcitation remain unclear. Subthreshold ion channels, including the A-type K +(I A) and the T-type Ca 2+(I T), are important mechanisms regulating the ability of neurons to generate firing activity, and changes in I Aactivity have been reported during hypertension. Thus, the first aim of the study focused on characterizing the basic biophysical and functional properties of I Ain presympathetic PVN neurons projecting to the rostral ventrolateral medulla (PVN-RVLM). Our studies demonstrated the presence of a functionally relevant I Ain PVN-RVLM neurons, which actively modulated the action potential waveform and firing activity. The second aim of the study was to determine whether alterations in the biophysical properties of I Acontributed to enhanced neuronal excitability of PVN-RVLM neurons during hypertension. Our studies indicated that diminished I Aavailability constituted a contributing mechanism underlying hyperexcitability in these neurons during hypertension. Previous studies have indicated an opposing balance between the subthreshold ion channels, I Aand I T. Thus, the final aim of the study assessed the biophysical competition between I Aand I T, and functionally addressed the influence of such balance on the activity of PVN-RVLM neurons under normal and hypertensive conditions. Our studies indicated that the balance between I (open full item for complete abstract)

Committee: Javier Stern (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2001, Medicine : Cell and Molecular Biology

The overall goal of these studies was to determine the nature of the signals used by circadian pacemaker located in the suprachiasmatic nucleus (SCN) to convey the time of day information to the rest of the organism. In these studies, we used the Syrian hamster as a model for investigating behavioral and autonomic outputs of the SCN. In the first part of the dissertation, a technique was developed to pre label fetal hypothalamic transplants and their efferents. This was done with the eventual aim of using this marker to correlate the pattern of outgrowth of fetal SCN grafts with the recovery of specific rhythms. The second part of the dissertation explored the role of SCN neural efferents in the control of circadian rhythms using knife cuts to create "SCN islands" within the hypothalamus. Rhythms in activity, drinking, heart rate and body temperature persisted after knife cuts that isolated the SCN and interrupted its projections, suggesting that neural efferents are not necessary for these rhythms and cons istent with evidence of a diffusible signal emitted from the SCN. The third and final part of the dissertation examined the ability of fetal SCN grafts to restore multiple rhythms to SCN-lesioned, arrhythmic hosts. Circadian mutant hamsters were used as either hosts or donors, allowing us to unambiguously attribute restored rhythms to the presence of the grafted tissue. In a majority of recipients, fetal SCN grafts simultaneously restored multiple rhythms in activity, drinking, heart rate and body temperature. Together, these studies confirm the role of the SCN in the generation of these diverse behavioral and autonomic rhythms, as well as suggest that a diffusible signal may be responsible for conveying circadian information to the rest of the organism.

Committee: Michael Lehman (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2000, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience)

Axonal growth is reduced with aging in several models of brain plasticity. These reductions are assumed to contribute to corresponding reductions in behavioral plasticity that occur with aging. Specifically of interest was whether the aged brain is a less permissive substrate for axonal growth in the absence of injury. To assess the baseline substrate properties of the aged brain, explants of sympathetic ganglia were cultured onto cryostat sections of young and aged forebrain and the extent of neurite outgrowth from these explants was measured. The extent of growth varied significantly between brain regions but was not reduced with aging. These data suggest that age-related reductions in axonal growth within the brain are due to age-related changes in the interactions between living cells rather than reduced baseline substrate properties. Axonal regeneration is limited in the CNS following injury. Previous investigations have identified axon-growth inhibitors associated with myelin, inspiring the hypothesis that myelinated fiber tracts cannot support axonal growth. Other studies, however, have shown that white matter can support axonal growth in vivo. We sought to reconcile these contrasting lines of evidence by reassessing the capacity of white matter in cryostat sections of brain and spinal cord to support neurite growth from cultured sympathetic neurons. White matter was found to support long neurite growth oriented in parallel with the fiber tract and inhibit non-parallel growth. This geometric growth constraint is likely due to myelin-associated inhibitors since neurites extending on myelin-deficient tracts or on myelinated tracts in the presence of factors known to deactivate these inhibitors were significantly less parallel. To assess the effects of injury-induced tissue disruption on axonal growth in the absence of glial scarring, spinal cord or sciatic nerve was crushed and immediately frozen to prevent glial scarring. When longitudinal cryostat sections we (open full item for complete abstract)

Committee: Keith Crutcher, Ph.D (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2007, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

Background: The use of (+)-methamphetamine (MA) has been shown to result in long-term monoamine, creatine, corticosterone, and cognitive alterations in human users. Previous animal models of MA exposure have demonstrated persistent damage to monoaminergic systems; but few cognitive effects have been shown. Additionally, the effects of MA on corticosterone and creatine have not been highly investigated. Methods: In Experiment-1, adult rats were treated with one of two MA dosing regimens and evaluated for neurotoxicity and behavior. Experiment-2 examined the influence of test order and treatment-to-test interval on cognitive outcomes. Experiment-3 determined the effects of MA on creatine, monoamines, and corticosterone up to 72 h after the first dose. Additionally, Experiment-3 was designed to evaluate the corticosterone-releasing effects of MA by utilizing a known stressor in an experiment similar to the one above. Finally, Experiment-4 examined the relationship between corticosterone and the MA-induced cognitive changes by determining the effects of MA in adrenalectomized rats on neurotoxicity and behavior. Results: The dose frequency utilized in these studies had no differential effects on behavior or neurotoxicity; however, impaired path integration and spared spatial navigation was demonstrated after MA administration. Removal of potential influences from other behavioral tasks and a shorter treatment-to-test interval did not alter the lack of spatial learning deficits. Corticosterone was increased up to 72 h and monoamine levels were decreased as early as 7 h after the first dose of MA, whereas brain creatine levels were unaffected. The alterations in neurochemistry did not appear to be the result of MA-induced increases in corticosterone alone; forced swim increased corticosterone but did not resemble MA in the other measurements. Blockade of corticosterone after MA treatment demonstrated that the deficits in path integration are not due to the increase in cort (open full item for complete abstract)

Committee: Dr. Michael Williams PhD (Committee Chair); Charles Vorhees PhD (Other); Ton Degrauw MD, PhD (Other); Kim Seroogy PhD (Other); Gary Gudelsky PhD (Other) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2006, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

An emerging model is that CNS fuel sensors, such as AMP kinase (AMPK) and the mammalian target of rapamycin (mTOR), integrate signals from stored and immediately available fuels, and in turn regulate food intake. The experiments described in this dissertation focus on novel CNS fuel sensing mechanisms by which fatty acid derivatives and compounds that affect fatty acid metabolism modulate food intake. Oleoylethanolamide (OEA), a derivative of oleic acid synthesized in the intestine following refeeding, reduces food intake. OEA shares similarities with other nutrient-derived hormones that signal energy status to the CNS, but its mechanisms of action remain unclear. We tested whether OEA-induced anorexia occurs through specific interactions with hormones that modulate food intake through CNS pathways involved in energy homeostasis, or is rather due to unspecific behaviors. Our results indicate that OEA suppresses feeding without causing visceral illness, and that neither ghrelin, PYY, GLP-1, apo A-IV nor CCK play a critical role in this effect. OEA is not the only fatty acid metabolism related compound that suppresses food intake. C75 is a fatty acid synthase inhibitor that inhibits food intake via direct actions in the CNS. MTOR, a member of the phosphatidylinositol kinase-related protein kinase family, plays a crucial role in nutrient sensing and the control of protein synthesis. Its inhibition stimulates food intake in rats. We hypothesized that C75-induced anorexia depends on its ability to activate the mTOR pathway in the hypothalamus. Consistent with this hypothesis, C75 increases the phosphorylation of key components of the mTOR pathway and inhibitors of mTOR reverse C75-induced anorexia. Previous work showed that C75 is ineffective when rats are on a ketogenic diet. Consistent with a role for mTOR in mediating the effects of C75, C75-induced anorexia and activation of the mTOR pathway were abolished in rats maintained on a ketogenic diet. Together, these data (open full item for complete abstract)

Committee: Dr. Randy Seeley (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2006, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

±3,4-Methylenedioxymethamphetamine (MDMA) is a popular drug of abuse that produces long-term decreases in neurochemical markers of 5-HT that are believed to be indicative of selective toxicity to the 5-HT nerve terminal. A potential mechanism underlying this proposed neurotoxicity involves reactive nitrogen species. In vivo microdialysis studies demonstrated that MDMA increases extracellular nitrite/nitrate (NOx), a marker of NO, and that this is iNOS dependent. However, iNOS-dependent MDMA-induced NOx formation is unrelated to long-term 5-HT toxicity, as iNOS inhibition had no effect on long-term MDMA-induced 5-HT depletion. Histological evidence of MDMA-induced 5-HT nerve terminal damage is inconsistent. Antibodies to the cleaved form of the microtubule associated protein tau (C-tau) were used to characterize neurotoxicity produced by psychostimulant drugs. Amphetamine (AMPH) and methamphetamine (METH), both DA-depleting compounds, produced an increase in C-tau immunoreactivity, whereas the 5-HT-depleting drugs MDMA, para-methoxyamphetamine (PMA) and the prototypic 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) did not. C-tau was localized to astrocytes, not neurons, suggesting that C-tau is not a direct marker of neuronal damage, but may be an alternative indicator of reactive gliosis. Furthermore, these data are in agreement with previous findings that AMPH and METH produce reactive gliosis, whereas MDMA, PMA and 5,7-DHT do not. Human users of MDMA have reported cognitive/behavioral deficits following chronic use, including impaired sexual function and reduced sexual motivation. In the rat, prior treatment with MDMA may alter the rewarding properties of other drugs of abuse. Given the potential similarities in neural pathways mediating the rewarding properties of drugs and sex, studies were designed to assess the effect of MDMA on the response to a natural reward, i.e., sex, in the conditioned place preference (CPP) paradigm. Rats treated with a 5-HT-depletin (open full item for complete abstract)

Committee: Dr. Gary Gudelsky (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2006, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

Opioid peptides have long been known to have regulatory effects on sexual behavior. Endogenous opioids affect reproductive function in both men and women, and the effects of exogenous opioid use are often described in sexual terms as an “orgasmiclike” euphoria. Moreover, long-term opioid use results in a deterioration of sexual function. Studies have shown similar regulatory effects on sexual behavior in rodent models, in which opioids facilitate sexual motivation and inhibit sexual performance. Of the three opioid receptors (mu, delta, and kappa), anatomical, gene manipulation, and pharmacological evidence show mu opioid receptors to be the most likely involved in the regulation of sexual behavior. The goal of this dissertation was to elucidate the role of endogenous opioid peptides in the regulation of male sexual behavior by addressing the following three specific aims. Specific aim 1 addressed when and where endogenous opioid peptides act during sexual behavior. This aim was investigated by examining in which brain regions mating-induced mu opioid receptor activation occurs and during which component of sexual behavior it occurs. Specific aim 2 addressed what the behavioral significance of mu opioid receptor activation is. The medial parvocellular Subparafascicular thalamic nucleus was the brain region chosen for examination of this aim. This region is part of the spinothalamic pathway important for the processing of sensory signals related to ejaculation. Sexual behavior was observed following pharmacological mu opioid receptor activation in the medial parvocellular Subparafascicular thalamic nucleus. Specific Aim 3 addresses which endogenous opioid peptide(s) is acting during male sexual behavior. Although three known ligands exist for mu opioid receptors, we chose to begin investigation of this aim by examining beta-endorphin. Activation of beta-endorphin neurons following various components of sexual behavior was analyzed. In addition, sexual behavior of bet (open full item for complete abstract)

Committee: Dr. Lique Coolen (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2006, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

The hypothalamo-pituitary-adrenocortical (HPA) axis is a final regulator of stress responses, which are activated by non-specific stressful stimuli. Albeit acute activation of the HPA axis is protective to fight against noxious stimuli, prolonged activation can be deleterious. Glucagon-like peptide-1 (7-36) amide (GLP-1) is an insulinotropic intestinal peptide, which is also expressed in brain. GLP-1 expression in brain is restricted in the nucleus of solitary tract and the ventrolateral medulla of the brainstem. GLP-1 nerve fibers innervate widely in brain. Centrally infused GLP-1 is known to activate the HPA axis. Thus, in this dissertation, we aimed to understand the role of GLP-1 in stress. First, the GLP-1 system in stress circuitry was investigated using immunohisochemical methods. We found heavy GLP-1 innervation of hypothalamic neurons expressing corticotropin releasing hormone, and oxytocin, as well as preautonomic neurons projecting the brainstem. There was scarce innervation of argininvasopressin expressing neurons. The distribution suggests that GLP-1 activates the HPA axis not only directly, but can also modulate it via other systems. Next, we monitored a regulation of GLP-1 gene expression by acute stress. In situ hybridization was performed using riboprobes generated by targeting mRNA and intronic RNA. We found that GLP-1 messenger level is quickly down-regulated after stress. In addition, intronic RNA expression revealed that the activation was restricted to the lateral area of the nucleus of solitary tract, which projects to the paraventricular nucleus of thalamus. Furthermore, we tested the role of GLP-1 in chronic stress. We found that GLP-1 is required for animals to develop a chronic stress-induced facilitated response to a novel stressor. In addition, GLP-1 systems interacted with stress to reduce body weight. Finally, as an effort to elucidate possible mechanisms for the interaction between chronic stress and GLP-1, the anorectic effects of GL (open full item for complete abstract)

Committee: Dr. James Herman (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2006, Medicine : Molecular and Developmental Biology

3,4-Methylenedioxymethamphetamine (MDMA) is a ring substituted amphetamine similar in structure to mescaline. Exposure to MDMA from postnatal days (P)11-20 has been shown to induce deficits in spatial learning and memory as well as in path integration learning when the animals are tested as adults. These learning and memory deficits emerge at P30 and persist until P360. This dosing regimen has been shown to decrease serotonin and alter serotonin signaling in the adult brain; however these effects were independent of the learning and memory deficits observed. Finally, dosing on P11 has been shown to increase corticosterone levels during the stress hyporesponsive period, a time when there are attenuated CORT levels. While these areas appear to be important in elucidating the mechanisms underlying MDMA, it is important to investigate systems that may not have been previously implicated in MDMA pharmacology. Microarray analysis revealed 71 genes with altered expression (66 up-regulated and 5 down-regulated) in the hippocampus of adult animals treated from P11-20 with MDMA. Real-time PCR analysis verified 8 out of the 24 genes selected for verification. The 8 verified genes were examined in the striatum of adult animals, with the gene encoding angiotensinogen (AOGEN) up-regulated approximately 75%. Following examination in the hippocampus and striatum, the 8 verified genes were examined in the hippocampi of P12 and P21 MDMA-exposed animals. In P12 animals, nuclear orphan receptor 1 was up-regulated by ~600% and AOGEN was down regulated by 50%; while AOGEN was up-regulated by 3 fold on P21. One gene was selected for further investigation. CAPON, the gene that showed the highest up-regulation during microarray analysis, was analyzed with common pathway members nNOS, PSD-95, and the NMDA receptor subunit 1 (NR1). While CAPON protein was unchanged, the remaining proteins were increased in the dentate gyrus of adult animals. Together with the protein changes associated with N (open full item for complete abstract)

Committee: Dr. Charles Vorhees (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2006, Medicine : Cell and Molecular Biology

Expression of the human epidermal growth factor receptor (EGFR) in murine Schwann cells provides a simplified model of early peripheral nerve pathologies that manifest in neurofibromatosis type 1 (NF1). EGFR+ mice develop Schwann cell hyperplasia, mast cell infiltration, nerve hypertophy, collagen deposition, and loss of axon-glial interactions. Historically, mast cells have been viewed as effector cells in allergy and inflammation, but a growing body of literature suggests that they play vital roles in tissue homeostasis and the development of numerous pathologies. The major objective of this work was to explore the contribution of mast cells to the nerve pathology of EGFR+ mice. The first set of studies demonstrates that mast cell degranulation is necessary for the development of NF1-related nerve pathology in EGFR+ mice by genetic mast cell ablation, mast cell reconstitution via bone marrow engraftment, and pharmacologic mast cell stabilization. We show that EGFR+ mutant nerve upregulates the expression of several mast cell chemoattractants, which may serve to recruit or activate mast cells, and together, these cells drive peripheral nerve disruption. In the second set of studies, we attempt to define which mast cell mediators, released upon degranulation, drive nerve pathology. We outline a possible pathologic role for NGF and histamine, and conclude that several other mediators may also contribute to nerve pathology. In all, this work defines a pathologic role for mast cells in the development of EGFR+ nerve pathology, supports continued investigation of mast cells in Nf1 model systems, and suggests a possible role for global mast cell stabilizers in the treatment of NF1 patients.

Committee: Dr. Nancy Ratner (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2005, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

Reward and reward-based learning are regulated by the limbic system. Repeated exposure to rewarding stimuli has been shown to lead to addictive behavior, and this conversion is hypothesized to be a dependent on learned cues. In this thesis, reward-based learning was tested using male sexual behavior as a model system. Male sexual behavior is a type of natural rewarding behavior that activates various structures within the limbic system. Gaining sexual experience in the rodent is associated with responding to female associated cues leading to increased anticipation of the female and more efficient copulatory behavior. In particular, sex behavior – as well as sex related environmental cues – have been shown to increase neural activation of limbic structures including the nucleus accumbens (Nacc), ventral tegmental area (VTA), and medial prefrontal cortex (mPFC). In an initial set of experiments, the role of the mPFC was examined for an ability to regulate the acquisition and expression of male sexual behavior. In a separate experiment, the role of the mPFC for conditioned aversion to sex behavior was tested. Lesions of the mPFC did not alter the acquisition or expression of male sexual behavior. However, lesions did affect the ability to abstain from sex behavior once it had been paired with aversion. These data suggest that the mPFC is not necessary for the execution of male sexual behavior, but is necessary for behavioral inhibition. In a second set of studies, three separate experiments were conducted to better understand how naturally rewarding behaviors impact limbic system function. To do this, the effects of repeated sex behavior on the function, morphology, and molecular regulation of the mesocorticolimbic system were investigated in a separate set of experiments. Thus, in addition to investigating the role of the mPFC for the acquisition and expression of the behavior, how sex behavior affects the morphology, function, and transcriptional profile of structure (open full item for complete abstract)

Committee: Dr. Lique Coolen (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2005, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

This thesis explored the functional and anatomical basis for corticotropin releasing factor (CRF) mediated analgesia within the periaqueductal gray (PAG) of the rat. CRF mediated analgesia was tested using the tail flick latency test and the hot plate test. We found that CRF dose dependently increased tail flick latencies in anesthetized rats when injected into the ventral PAG. CRF increased hot plate latencies in a manner that was attenuated by a CRF receptor antagonist, alpha helical CRF(12-41) in awake rats. Our second goal was to determine the likely source of CRF into the PAG. Therefore, the next section of this project utilized a retrograde neuronal tract tracer, cholera toxin beta subunit combined with immunolocalization of CRF. We found that the bed nuclei of the stria terminalis (BNST), the central nucleus of the amygdala (CEA), and the paraventricular nucleus of the hypothalamus (PVH) all contained projection neurons to the PAG that also contained CRF. CRF varicosities also terminated on or near retrogradely labeled cells that project to the PAG. This was seen throughout numerous pain processing regions in the forebrain that send afferent projections to the PAG. Taken together, this suggests that CRF may modulate the activity of PAG neurons directly, indirectly, or likely a combination of the two. Finally, the functional activity of the BNST to PAG connection was electrophsyiologically explored. The response of PAG neurons to either electrical or chemical orthodromic stimulation of the BNST was determined. Post stimulus time histograms were recorded following 1 Hz stimulation and compared to the results following 100 Hz stimulation. Additionally, glutamate and CRF were injected into the BNST and the subsequent response of PAG neurons was recorded. Inhibition of PAG activity was the overwhelming response to either electrical or chemical stimulation. In summary, we found that CRF mediated analgesia in the PAG is dose dependent and specific for CRF receptors. (open full item for complete abstract)

Committee: Dr. Michael Behbehani (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2005, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

Exposure to stress elicits behavioral and physiological responses in animals and humans, including changes in food intake and body weight. This dissertation uses a unique animal model of social stress, the Visible Burrow System (VBS), to study the effects of stress on energy homeostasis. The experiments presented in this dissertation are the first systematic studies to examine social stress-induced changes in energy homeostasis in the VBS and lay the groundwork for understanding stress-related metabolic alterations and disorders. Male rats in mixed-gender rat colonies form dominance hierarchies when housed in the VBS. Subordinate (SUB) males consistently lose a significant amount of body weight over 14 days in the VBS, while dominant (DOM) males maintain or lose very little weight. Food intake was measured while the animals were in the VBS by the AccuDiet ID system (AccuScan Instruments, Columbus, OH, USA). SUB were hypophagic throughout the 14-day VBS housing period during which body composition analysis showed that both DOM and SUB lost adipose tissue, but SUB lost lean tissue as well. After social stress, SUB have elevated corticosterone and decreased testosterone compared to CON and DOM. During recovery SUB were hyperphagic on a standard chow diet and re-gained body weight primarily as adipose tissue and this is further exacerbated by repeated exposures to social stress and recovery. Consistent with body composition analyses, SUB were hyperinsulinemic and hyperleptinemic compared to DOM and CON after VBS stress and recovery. In addition, SUB had a higher proportion of adipose tissue in the visceral fat depot compared to CON and DOM. While there were no differences among the groups in an oral glucose tolerance test prior to stress, after 2 cycles of VBS stress and recovery both DOM and SUB groups had become more efficient at clearing the glucose load compared to CON irrespective of their differences in body composition. Together these data suggest that neurochemi (open full item for complete abstract)

Committee: Dr. Randall Sakai (Advisor) Subjects: Biology, Neuroscience

MS, University of Cincinnati, 2004, Arts and Sciences : Biological Sciences

The mouse main olfactory bulb (MOB) is commonly used as a mammalian model to study olfactory processing. The genetic techniques available with the mouse make its MOB a powerful model. Therefore, an objective of this study was to develop an in vivo mouse preparation for recording from the MOB. An aim was to establish a protocol using an injectable anesthetic such as chloral hydrate. Another aim was to develop a protocol to record the spontaneous activity of antidromically identified mitral cells in mouse in vivo with extracellular electrophysiological techniques. Currently, such a protocol does not exist. Mitral cell single-units were identified by antidromic activation from the posterior piriform cortex, and their spontaneous activity was recorded for more than 1800s. Also, this protocol was stable enough to record from single-units while pharmacological agents were applied to the surface of the MOB. However, the amount of chloral hydrate required to maintain a surgical plane of anesthesia was linearly correlated with a decrease in MOB spontaneous activity and could be lethal. The negative effects of chloral hydrate were exacerbated in the inbred mouse C57BL/6L. Therefore, analgesic supplements to chloral hydrate anesthesia were investigated. Supplementation with buprenorphine, a synthetic m-opioid receptor agonist, was problematic. Buprenorphine at doses of 0.02, 0.05, and 0.2 mg/kg reduced spontaneous activity of bulbar neurons by 19, 45, and 54%, respectively. In contrast, ketoprofen, a non-steroidal anti-inflammatory with reported analgesic activity, did not inhibit spontaneous activity at doses of 100 or 200 mg/kg. Importantly, mice given 100-mg/ kg ketoprofen at the beginning of an experiment, before surgery, required significantly less chloral hydrate than control animals. Animals in both groups were maintained at a surgical plane of anesthesia using the EEG and the hindpaw withdrawal response. Lastly, ketoprofen altered both the EEG trace and power spectrum (open full item for complete abstract)

Committee: Dr. Edwin Griff (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2004, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

Brain dopamine signaling is important for regulation of a variety of complex functions, including locomotor activity, cognition, motivation, and emotion. In particular, abnormalities in dopamine signaling have been implicated in psychiatric disorders, including psychotic disorders, such as schizophrenia, and substance abuse and addiction. The D3 dopamine receptor is of particular interest due to its restricted localization in limbic brain regions, which are associated with motivation and emotion, and to its apparently inhibitory role in regulating cellular and behavioral responses to dopamine. However, a clear understanding of the functional role of the D3 receptor has been hampered by a lack of sufficiently selective pharmacological tools. The aims of these studies were to clarify the role of the D3 receptor in rodent behaviors by establishing appropriate conditions for the use of currently available agonists, assessing the behavioral effects of new, highly selective antagonists, and examining relationships between D3 receptor expression and individual differences in behavior. In the first set of studies, the effects of preferential D3 receptor agonists on mouse locomotor behavior were assessed. When administered prior to placement in a novel environment, these agonists inhibited locomotor activity in wild-type mice, but not those lacking functional D3 receptors, suggesting that the behavioral effects were mediated by D3 receptors. Additionally, these compounds were without effect in mice that had been acclimated to the testing chamber prior to drug administration. These results suggest that D3 receptor stimulation is inhibitory to novelty-stimulated locomotion and establish appropriate conditions for selective D3 receptor activation in vivo. In the second set of studies, the behavioral effects of a highly-selective D3 receptor antagonist were assessed. This antagonist stimulated basal locomotor activity and enhanced amphetamine-stimulated locomotion in wild-type, (open full item for complete abstract)

Committee: Dr. Neil Richtand (Advisor) Subjects: Biology, Neuroscience

MS, University of Cincinnati, 2004, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience)

Excitatory and inhibitory signals are summated at the paraventricular nucleus of the hypothalamus (PVN) and translated into a decision to initiate the hypothalamic pituitary adrenocortical (HPA) axis response to stress. The mechanism of action behind this initiation is still unknown, but the excitatory neurotransmitter glutamate is suspected to play a role. Glutamate receptors have been localized to PVN neurons. Ionotropic glutamate receptors (iGluRs) containing the GluR5 subunit have been localized to the region of the PVN known to initiate the HPA axis. The present study is a test of the hypothesis that iGluRs containing the GluR5 subunit are involved in activation of the HPA axis. We investigate this through microinfusion of a GluR5 agonist (ATPA), and antagonist (LY382884), directly into the PVN. We found that both LY382884 and ATPA activate the HPA axis, and suggest that these compounds may be functioning on fundamentally different receptors at different neuroanatomical locations.

Committee: Dr. James Herman (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2003, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience)

The nucleus accumbens is a key limbic region implicated in mechanisms underlying reward and addiction. Evidence for involvement of the Nacc in responses to drugs of abuse (including cocaine and morphine) has partly come from studies using Fos as a marker for neuronal activation. While previous reports have consistently shown that Nacc neurons are activated following acute administration of cocaine, studies of morphine-induced activation have produced variable results. In the present study, we used two markers of neural activation, phosphorylation of the MAP-kinase, ERK, and expression of Fos, to investigate Nacc activation in response to either cocaine or morphine. In addition, we used a combination of retrograde tract tracing and immunocytochemistry to investigate whether activated Nacc neurons send projections to the ventral pallidum (VP), a major efferent target of the Nacc. Whereas cocaine induced neural activation at ten minutes, one hour, and two hours following drug administration, morphine only induced activation two hours following injection. Furthermore, while cocaine-activated neurons were present at all rostral-caudal Nacc levels, morphine-activated neurons were restricted to the rostral Nacc. Finally, cocaine induced activation of a subset of VP-projecting neurons in all rostral-caudal levels of the Nacc, while morphine did not. Thus, cocaine and morphine induce different temporal and regional patterns of activation in the Nacc, with cocaine producing more rapid and widespread activation than morphine. The only area of overlap in the patterns of activation produced by either drug was in the rostral Nacc, suggesting that this subdivision may be particularly important in reward and addiction.

Committee: Dr. Michael Lehman (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2003, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience)

Gonadotropin releasing hormone (GnRH) neurons play a central role in the control of mammalian reproductive function. Changes in the pulsatile secretion of GnRH and luteinizing hormone (LH) are critical for the regulation of events leading to ovulation, as well as to inhibition of ovulation prior to puberty and during other physiological periods of infertility. Based on recent data, we have developed a working hypothesis for the control of pulsatile GnRH/LH secretion by endogenous opioid peptides (EOP). This hypothesis states that one of the EOP systems in the brain, the dynorphin-kappa receptor system, mediates the inhibitory effect of progesterone on GnRH pulse frequency during the luteal phase of the ovine estrous cycle. We first tested one prediction of this hypothesis by determining whether or not dynorphin neurons contain progesterone receptors. We found that a very high percentage of dynorphin neurons in the arcuate nucleus of the hypothalamus, as well as in the anterior hypothalamic area and the preoptic area, contained immunoreactive nuclear progesterone receptors. We then asked whether or not progesterone could act upon these neurons to increase the transcription of dynorphin by using in situ hybridization to measure changes in the levels of mRNA encoding the precursor for dynorphin. We found that ovariectomy significantly decreased the number of PPD mRNA-expressing cells in the ARC, POA and AHA; progesterone replacement increased the number of cells back to those levels seen in intact luteal phase animals in the POA and AHA but not in the ARC, suggesting that in the latter nucleus, estradiol also plays a role in maintaining dynorphin levels. In the same experiment CSF dynorphin was found to be elevated in the progesterone treated group. We further determined that a very large proportion of dynorphin cells colocalize another neuropeptide, neurokinin B, previously shown to be sexually dimorphic and contain estradiol receptors. Finally, we implicated a novel (open full item for complete abstract)

Committee: Dr. Michael N. Lehman (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2003, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience)

The suprachiasmatic nucleus (SCN) has long been recognized as the anatomical locus of the mammalian circadian pacemaker. Despite recent advances in the understanding of the molecular mechanisms, it remains unclear how the tissue level properties of the SCN contribute to the function of the SCN as the “master” oscillator of the circadian system. Chapter 2 of this thesis provides a review of the heterogeneity that is inherent to the structure and function of the SCN. The SCN can be viewed as a multi-component structure, with its endogenously rhythmic properties localized to regions of the nucleus that form a “shell” appearance, and the non-rhythmic and light-responsive properties largely overlapping in a central region of the nucleus, forming a “core” appearance. Chapter 3 provides evidence of how the patterns of rhythmic MAP kinase phosphorylation in hamsters contribute to this view of SCN organization. In characterizing the two rhythms of phophorylated MAP kinase (pERK) in the SCN, we further discovered that the presence of the eye is necessary for one rhythm to persist, as enucleation abrogated pERK in the core region. The neurochemical phenotype of pERK cells and their involvement in putative intercellular interactions were then characterized in chapter 4. In chapter 5, the role of retinal activity in mediating the eye's influence on the core pERK rhythm was demonstrated using the sodium-channel inhibitor, tetrodotoxin. Finally, in chapter 6, I have provided evidence that the expression of a clock gene, Per1, is also influenced by ocular input, as enucleation resulted in changes of its immunoreactivity within the hamster SCN. Together, these studies provide anatomical evidence of a role for the eye in influencing circadian properties of the SCN that is distinct from its role in transducing photic information.

Committee: Dr. Michael Lehman (Advisor) Subjects: Biology, Neuroscience

PhD, University of Cincinnati, 2003, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience)

Following a nerve injury, there is evidence that there is a large increase in the level of spontaneous firing in the afferent neurons linked to the injury site. The development of this ectopic activity may be particularly important for the development of hyperalgesia, allodynia and ongoing pain associated with nerve injury. In the present study, the relationship between ectopic activity at the very beginning of peripheral nerve injury and neuropathic pain behavior (thermal hyperalgesia and mechanical allodynia) was examined. We used either chronic constriction injury (CCI) or spare nerve injury (SNI) on the sciatic nerve to produce neuropathic pain in rats. In some animals, the injured nerve activity was blocked initially with either bupivacaine or TTX for 5-7 days and 24 hours per day. Animal neuropathic pain behaviors, thermal hyperalgesia and mechanical alodynia, were checked from the first to 2 to 5 months post operation. During this time, there were no significant neuropathic pain behaviors observed on the rats with sciatic nerve injury and initial nerve blockade. We also checked the ectopic activity in rat sciatic nerve with CCI. Initial nerve blockade prevented the subsequent ectopic activity in injured nerve. However, 10 days following CCI or SNI, when rats already presented robust thermal hyperalgesia and mechanical allodynia, this blockade only relieved naturopathic pain temporarily during the blockade. These results suggested that ectopic activity occurring at the early stage of peripheral nerve injury was essential for the development of chronic neuropathic pain.

Committee: Dr. Lei Yu (Advisor) Subjects: Biology, Neuroscience