Exposure to certain stressors during a sensitive period around puberty can lead to enduring effects on an animal’s response to estradiol. In estradiol-influenced behaviors, such as sexual receptivity, hippocampal-dependent learning and memory, depression-like behavior, and anxiety-like behaviors, exposure to a peripubertal stressor such as shipping stress or an injection of lipopolysaccharide (LPS) can eliminate or even reverse the normal response to estradiol. In addition to regulating these behaviors, estradiol play a role in the regulation of body weight. While some of the previous studies touched on short-term effects on body weight, no systemic long-term study of the effects of a peripubertal stressor on body weight, particularly without interruption by ovariectomy, have been undertaken. This paper introduces a hypothesis that proposes that increased adiposity following exposure to a peripubertal stressor leads to the changes to estrogen-dependent behaviors through altered levels of estrogens and changes to estrogen receptors. The first chapter examines body weight data collected during studies with other aims, and then proposes an experiment to test whether either of two peripubertal stressors results in increased weight gain and body weight. The following chapter proposes further experiments designed to determine the proximate mechanisms leading to weight gain following peripubertal stressors and the role of diet on weight gain. The final chapter proposes experiments to test the effects of adiposity on peripheral levels of testosterone, aromatase, estradiol, and estrone; central levels of estradiol and estrone; and estrogen receptors in the brain.

Rotating shift work, irregular sleep patterns and jetlag disrupt circadian rhythms, induce or aggravate disease, and produce deficits in cognitive function. Internal misalignment, a state in which abnormal phase relationships prevail between and within organs, is widely proposed to account for these adverse effects of circadian disruption. This hypothesis has been difficult to test because phase shifts of the entraining environmental cycle lead to transient desynchrony. Thus, it remains possible that phase shifts, regardless of internal desynchrony, account for adverse effects of circadian disruption. I have used the duper mutant hamster, whose locomotor activity rhythms re-entrain 5-fold faster than wild types after a phase shift of 8 hours, to test whether internal desynchrony can account for adverse effects of jet lag on adult neurogenesis. I subjected wild type and duper female hamsters to alternating 8h phase advances and delays of the LD cycle at 16-day intervals. I injected 5-Bromo-2’-deoxyuridine (BrdU, a thymidine analogue) after the 4th shift and collected brains after the 8th shift. As expected, mutants re-entrained activity rhythms more rapidly than did wild types. On the other hand, estrous cycles, as assessed by vaginal smears, were rarely disrupted by repeated phase shifts in either genotype. I next compared cell proliferation and neurogenesis in the subgranular zone of the hippocampus between Duper mutants and wild type siblings using the S-phase marker BrdU and the neuronal marker NeuN. I assessed the total number of BrdU cells in the subgranular zone of the hippocampus, as the proportion that expressed NeuN. Duper mutants had more BrdU-ir cells, and more BrdU+/NeuN+ cells than did wild types, whether or not they experienced phase shifts, revealing an unexpected increase in neurogenesis. Surprisingly, repeated phase shifts increased neurogenesis in WT but not duper hamsters. Despite the increase in neurogenesis, phase shifts reduced the number of adult-born non-neuronal (BrdU+/NeuN-) cells in WT hamsters but had no such effect on duper mutants. In addition, the duper mutation increases hippocampal neurogenesis regardless of circadian. Our results suggest that adult-born non-neuronal cells are most vulnerable to circadian disruption, and that internal desynchrony promotes their demise. disruption.

Major depressive disorder (MDD) is a leading cause of disability worldwide, with a lifetime prevalence rate of approximately 20%. Inadequate pharmacological treatment methods for MDD are a significant debilitating factor. Patient estimates suggest that the treatment resistance rate for pharmacological interventions is over 30%. Postmortem analyses of human tissue of individuals diagnosed with MDD have shown an increase in Poly (ADP-ribose) polymerase 1 (PARP-1) mRNA gene expression in prefrontal cortical white matter when compared to psychiatrically normal brain tissue. In order to further investigate this issue, the present study used the social defeat stress/chronic unpredictable stress (SDS + CUS) rodent model of depression to induce a state of chronic psychological distress. Rats were treated with either the PARP-inhibitor, 3-aminobenzamide (3-AB); a common selective serotonin reuptake inhibitor (SSRI) fluoxetine (FLX), or saline. During the stress manipulation we conducted the sucrose preference test, results revealed that saline-treated rats which had undergone SDS + CUS showed significant reductions in sucrose preference compared to all other groups. In addition, a social interaction test was conducted one day after the stress manipulation, and saline-treated stressed animals demonstrated less social interaction compared to all other groups, indicating the stress manipulation was effective. Neurobiological assays were conducted to examine PARP expression, microglial morphology, and proinflammatory cytokine expression. Though we expected to find a decrease, results from immunofluorescence studies of tissue sections revealed an elevation of PARP-1 protein expression in prefrontal cortical gray matter in the FLX/Stress group compared with SAL/Stress group. Microglial morphological changes indicated that the SAL/Stress group had significantly more prolate microglia when compared to all other treatment groups, suggesting early activation of microglia, an indicator of neuroinflammation. Increases in IL-1β and TNF-⍺ expression was observed in the hippocampus of the SAL/Stress group when compared to all other treatment groups. Interestingly, IL-6 expression was significantly elevated in the SAL/Stress group when compared to the FLX/Stress group and the CTRL/No stress group but did not significantly differ from the 3-AB/Stress group. This study revealed therapeutic potential of 3-AB for the treatment of stress-related disorders, as well as the neuroinflammatory mechanisms associated with chronic stress.

Peripubertal immune stress alters adult responsiveness to estradiol (E2) and progesterone (P). When female mice are injected with the bacterial endotoxin lipopolysaccharide (LPS) at six weeks of age, or during pubertal development, they display a decrease in response to ovarian hormones. In contrast, females ovariectomized prior to peripubertal immune stress display typical levels of sexual behavior following sequential injections of E2 and P in adulthood. Additionally, intact females exposed to peripubertal immune stress display a decrease in estrogen receptor alpha (ER-α)-immunoreactive (ir) cells in the medial preoptic area (MPOA) and ventromedial nucleus of the hypothalamus (VMH) in adulthood. However, ER-α has not been studied in mice that have been ovariectomized prior to receiving LPS. The objective of the present study is two-fold: to replicate the finding that ovariectomy prior to pubertal development prevents the deleterious effects of LPS administration, and to examine the status of ER-α in areas of the brain important to sex behavior. We predicted that mice ovariectomized after LPS injection would display fewer ER-α-ir cells and a decreased responsiveness to ovarian hormones than saline controls and those mice ovariectomized prior to LPS injection. To test this, female mice were ovariectomized or sham-operated prior to LPS treatment. Then, at six weeks of age, all mice were injected with saline or LPS. Following that, sham-operated mice were ovariectomized and ovariectomized mice were sham-operated. Mice were primed weekly with E2 and P, and sex behavior testing occurred once a week for 5 weeks. After the final behavior test, all mice were euthanized, their brains removed, and stained for ER-α via immunocytochemistry. Results revealed a large variability in hormone responsiveness. However, animals that received peripubertal LPS, but still had their ovaries, had significantly lower sexual receptivity when compared to animals that were ovariectomized prior to the pubertal period and given LPS. Further, there were no differences between groups in ER-α-ir numbers. External environmental stressors, such as animal housing and vibrations and noise from nearby construction, may have caused some of the results found here, which are inconsistent with previous findings.

We previously found that intermittent administration of 3,4-methylenedioxymethamphetamine (MDMA, “Ecstasy”) to adolescent male rats protected against the behavioral and serotonergic neurotoxic effects of a subsequent MDMA binge. Similar results have been reported for the dopamine (DA) neurotoxin methamphetamine (METH). The present study tested the hypothesis that intermittent adolescent MDMA exposure would protect against the DA neurotoxic effects of a METH binge. Male Sprague-Dawley rats were injected s.c. with MDMA (10 mg/kg x 2; 4-h interdose interval) or saline every fifth day from postnatal day (PD) 35 through PD 60. The animals were then challenged with either a low- or high-dose METH binge (4 or 8 mg/kg x 4; 2- h interdose interval) or saline on PD 67. Activity was measured 1 day after the binge, and regional serotonin transporter (SERT) and dopamine transporter (DAT) expression were analyzed at PD 74 by radioligand binding. All animals treated with METH on the challenge day became hyperthermic, independent of pretreatment conditions. Both MDMA-pretreated and drug-naïve rats also showed a dose-dependent hypoactivity 24 h after the first dose of the METH binge. The SERT binding results indicated that adolescent pretreatment with MDMA provided full or partial protection (depending on the brain region) against the serotonergic deficits produced by METH in previously drug-naïve animals. In contrast, MDMA pretreatment failed to protect against METH-induced decreases in striatal DAT binding. These results suggest that the neuroprotective 2 effects of adolescent MDMA pretreatment are confined to the serotonergic system, possibly reflecting a selective upregulation of antioxidant mechanisms in that system.

Dopamine is an important neurotransmitter in the brain, where it plays a regulatory role in the coordination of movement and cognition by acting through two classes of G protein-coupled receptors to modulate synaptic activity. In addition, it has been shown these two receptor classes can exhibit synergistic or antagonistic effects on neurotransmission. However, while the pharmacology of the mammalian dopamine receptors have been characterized in some detail, less is known about the molecular pathways that act downstream of the receptors. As in mammals, the soil nematode Caenorhabditis elegans uses two classes of dopamine receptors to control neural activity and thus can serve as a genetic tool to identify the molecular mechanisms through which dopamine receptors exert their effects on neurotransmission. To identify novel components of mammalian dopamine signaling pathways, we conducted a genetic screen for C. elegans mutants defective in exogenous dopamine response. We screened 31,000 mutagenized haploid genomes and recovered seven mutants. Five of these mutants were in previously-identified dopamine signaling genes, including those encoding the Ga proteins GOA-1 (ortholog of human Gao) and EGL-30 (ortholog of human Gaq), the diacylglycerol kinase DGK-1 (ortholog of human DGK0), and the dopamine receptor DOP-3 (ortholog of human D2-like receptor). In addition to these known components, we identified mutations in the glutamate-gated cation channel subunit GLR-1 (ortholog of human AMPA receptor subunits) and the class A acetycholinesterase ACE-1 (ortholog of human acetylcholinesterase). Behavioral analysis of these mutants demonstrates that dopamine signaling controls acetylcholine release by modulating the excitability of the cholinergic motor neurons in C. elegans through two antagonistic dopamine receptor signaling pathways, and that this antagonism occurs within a single cell. In addition, a mutation in the putative Rab GTPase activating protein TBC-4 was identified, which may suggest a role for this Rab GAP in synaptic vesicle trafficking. Subsequent behavioral and genetic analyses of mutants in synaptic vesicular trafficking components implicate RAB-3-mediated vesicular trafficking in DOP-3 receptor signaling. These results together suggest a possible mechanism for the regulation of dopamine receptor signaling by vesicular trafficking components in the cholinergic motor neurons of C. elegans.

No description available.

The olfactory system is a great model for studying regeneration due to the olfactory epithelium’s regenerative capability which makes it a potential a source of neural stem cells. The olfactory epithelium presents three types of cells: sustentacular cells which provide support and act as glial supporting cells; olfactory sensory neurons that are in charge of detecting odorant molecules in the air; and the stem cells that generated the aforementioned cell types. Olfactory sensory neurons are constantly dying and being replaced by new neurons originating from the stem cells that lie at the base of the olfactory epithelium. We have used an injury model that allows us to remove all the olfactory sensory neurons from the olfactory epithelium, via a single injection of methimazole. Then, at different timepoints after injury we measure the functional recovery of the olfactory epithelium by analyzing the expression of specific synaptic associated markers. Specifically, we analyzed the expression of synaptophysin, tyrosine hydroxylase, vesicular glutamate transporter 1, and vesicular glutamate transporter 2. Simultaneously, we measured glomerular size in order to serve as an indicator of anatomical recovery. Finally, we correlate these findings with previously generated data in the lab associated with functional recovery through behavior.

We have examined potential influences of gender, age, and nutrition on the expression of circadian locomotor activity rhythms in the flesh fly Sarcophaga crassipalpis. We found no significant differences in endogenous circadian period under constant dark conditions resulting from gender, nutrition, or age. Male and female flesh flies were predominantly diurnal under light-dark cycles, but their entrainment patterns differed. Females displayed higher activity levels and increasing activity with age, unlike males. Moreover, females exhibited an extraordinary, but transient, departure from diurnality which we characterize as “extended dark activity” (EDA), a continuous bout of locomotor activity extending three hours, or longer, into the dark phase at twice the median of the individual’s overall locomotor activity. EDA occurred as an age-dependent response to liver consumption. Our results suggest a linkage between physiological events associated with egg provisioning and locomotor activity as well as multiple influences on the expression of circadian clock-regulated behavior.

Cannabis is widely consumed by humans for pharmacological effects that are mediated by THC, though there is little evidence that THC is a primary reinforcer in non-human animal models. We hypothesized that THC may have potent reinforcement enhancing effects, comparable to other drugs (e.g., nicotine and caffeine) which are also widely consumed by humans, but difficult to establish as primary reinforcers in non-humans. In three experiments with male and female rats saccharin (SACC) or a visual stimulus (VS) served as reinforcers for operant behavior. We explored several pharmacological parameters of THC on responding for SACC or VS, including THC dose, intervals between THC injections and testing, and intervals between test sessions. THC acts as a reinforcement enhancer for both SACC and a VS across a range of doses and intervals. Daily THC injections systematically reduced behavior, possibly due to accumulation of THC bioavailability.