Matching Items (4)
Filtering by
Description
Monoamine neurotransmitters (e.g., serotonin, norepinephrine, and dopamine) are powerful modulators of mood and cognitive function in health and disease. We have been investigating the modulation of monoamine clearance in select brain regions via organic cation transporters (OCTs), a family of nonselective monoamine transporters. OCTs are thought to complement the actions of selective monoamine transporters in the brain by helping to clear monoamines from the extracellular space; thus, assisting to terminate the monoamine signal. Of particular interest, stress hormones (corticosterone; CORT) inhibit OCT3-mediated transport of monoamine, to putatively lead to prolonged monoamine signaling. It has been demonstrated that stress levels of CORT block OCT3 transport in the rat hypothalamus, an effect that likely underlies the rapid, stress-induced increase in local monoamines. We examined the effect of chronic variable stress (CVS) on the development of mood disorders and OCT3 expression in limbic and hypothalamic regions of the rat brain. Animals subjected to CVS (14-days with random stressor exposure two times/day) showed reduced body weight gain, indicating that CVS was perceived as stressful. However, behavioral tests of anxiety and depressive-like behaviors in rats showed no group differences. Although there were no behavioral effects of stress, molecular analysis revealed that there were stress-related changes in OCT3 protein expression. In situ hybridization data confirmed that OCT3 mRNA is expressed in the hippocampus, amygdala, and hypothalamus. Analysis of Western blot data by two-way ANOVA revealed a significant treatment effect on OCT3 protein levels, with a significant decrease in OCT3 protein in the amygdala and hippocampus in CVS rats, compared to controls. These data suggest an important role for CORT sensitive OCT3 in the reduction of monoamine clearance during stress.
ContributorsBoyll, Piper Savannah (Author) / Orchinik, Miles (Thesis director) / Conrad, Cheryl (Committee member) / Talboom, Joshua (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The purpose of the present study was to investigate seasonal changes in cell proliferation in the brains of adult American bullfrog. Our main question was whether there are seasonal differences in the proliferation and/or differentiation of newborn brain cells into arginine vasotocin- (AVT) or gonadotropin releasing hormone- (GnRH) producing neurons that might regulate bullfrog reproduction. . Bullfrogs in four distinct seasonal groups received injections of bromodeoxyuridine (BrdU), a thymidine analog that is taken up by dividing cells, and then euthanized six weeks later. Using doubleimmunofluorescence procedures to visualize BrdU and AVT or GnRH, we found no evidence for newborn AVT- or GnRH-ergic cells, but observed newborn cells in close proximity to AVT and GnRH cells. My project was a follow-up study to explore seasonal changes in adult cytogenesis related to AVT and GnRH terminal fields. GnRH fiber density fluctuated seasonally in the rostral pre-optic area (RPOA) and lateral septum (LS), and newborn cell numbers changed seasonally in the amygdala (AM) and RPOA. Seasonal differences in plasma testosterone concentrations were negatively related to GnRH fiber density in the LS. These results reinforce the seasonality of reproductive signaling and adult cytogenesis and support a role for seasonal steroid-peptide hormone interactions in modulating GnRH levels. Our results suggest a relationship between seasonal adult cytogenesis and reproduction, and set the stage for further research into the nature of this relationship.
ContributorsFehr, Tristan (Author) / Orchinik, Miles (Thesis director) / Deviche, Pierre (Committee member) / Talboom, Joshua (Committee member) / Barrett, The Honors College (Contributor)
Created2013-05
Description
The organic cation transporter 3 (OCT3) is a polyspecific monoamine transporter
found in the human and rat brain. In Rats, OCT3 is the only known monoamine transporter inhibited by physiological concentrations of corticosteroids. We hypothesized that CORT- mediated inhibition of OCT3 blocks the clearance of serotonin (5-HT) leading to an increase 5-HT receptor-mediated signaling. In experiment 1, due to conflicting reports on the location of OCT3 mRNA in the rat brain, in situ hybridization was performed on brain tissue sections. RNA was extracted from rat brain tissue, reverse transcribed into cDNA, and then polymerase chain reaction (PCR) was performed to generate riboprobe templates. The riboprobe templates were then used for in vitro transcription of digoxigenin (DIG)-labeled riboprobes complementary to OCT3. In experiment 2, 12 rats from an identical cohort were exposed to a chronic restraint stress paradigm (two hours/day for seven days, STRESS group), while the other 12 remained in their home cages (CTRL group). Twenty-four hours after the last stressor, all animals were euthanized and their brains immediately removed and frozen. Bilateral tissue punches were collected from 300μm coronal sections from the CA1 region of the dorsal hippocampus, basolateral amygdala (BLA), and dorsomedial hypothalamus (DMH). The relative OCT2, OCT3, and 5HT2a mRNA levels from each tissue punch were determined via quantitative real-time polymerase chain reaction (qPCR). The results of experiment 1 confirmed the presence of OCT3 mRNA in the CA1, amygdala, and the DMH. The results of experiment 2 show that chronic restraint stress did not alter gene expression for 5-HT2A, OCT2, and OCT3. These data may help reveal new information involving OCT3’s role in the hippocampus, amygdala and DMH in regards to localization and mRNA expression levels after exposure to a stressor.
found in the human and rat brain. In Rats, OCT3 is the only known monoamine transporter inhibited by physiological concentrations of corticosteroids. We hypothesized that CORT- mediated inhibition of OCT3 blocks the clearance of serotonin (5-HT) leading to an increase 5-HT receptor-mediated signaling. In experiment 1, due to conflicting reports on the location of OCT3 mRNA in the rat brain, in situ hybridization was performed on brain tissue sections. RNA was extracted from rat brain tissue, reverse transcribed into cDNA, and then polymerase chain reaction (PCR) was performed to generate riboprobe templates. The riboprobe templates were then used for in vitro transcription of digoxigenin (DIG)-labeled riboprobes complementary to OCT3. In experiment 2, 12 rats from an identical cohort were exposed to a chronic restraint stress paradigm (two hours/day for seven days, STRESS group), while the other 12 remained in their home cages (CTRL group). Twenty-four hours after the last stressor, all animals were euthanized and their brains immediately removed and frozen. Bilateral tissue punches were collected from 300μm coronal sections from the CA1 region of the dorsal hippocampus, basolateral amygdala (BLA), and dorsomedial hypothalamus (DMH). The relative OCT2, OCT3, and 5HT2a mRNA levels from each tissue punch were determined via quantitative real-time polymerase chain reaction (qPCR). The results of experiment 1 confirmed the presence of OCT3 mRNA in the CA1, amygdala, and the DMH. The results of experiment 2 show that chronic restraint stress did not alter gene expression for 5-HT2A, OCT2, and OCT3. These data may help reveal new information involving OCT3’s role in the hippocampus, amygdala and DMH in regards to localization and mRNA expression levels after exposure to a stressor.
ContributorsTompkins, Heather Camila (Author) / Orchinik, Miles (Thesis director) / Neisewander, Janet (Committee member) / Talboom, Joshua (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2013-05
Description
Schizophrenia is a debilitating psychiatric disorder with poorly understood genetic and environmental factors. An allelic variant of complement component 4 (C4), a protein first identified in innate immune response is strongly associated with schizophrenia. In the brain, activity of C4 leads to dendritic pruning, a process that may be causal in disease progression. Environmental factors, such as early life exposure to significant stressors also associate with increased risk of schizophrenia in later life. My hypothesis is that these factors do not act independently, but rather in tandem to influence disease etiology.
This hypothesis is supported by previous studies demonstrating that stress-induced elevation of glucocorticoids increases the transcription of C4. I propose that activated glucocorticoid receptors directly increase C4 protein expression as a transcription factor activator. Additionally, I propose that activated glucocorticoid receptors inhibit the expression of the transcription factor nuclear factor-light-chain-enhancer of activated B cells (NF-κB), thereby leading to decreased expression of the C4 inhibitor CUB and Sushi multiple domains 1 (CSMD1).
Glucocorticoid receptors and C4 are richly expressed in the hippocampus, a region critical in memory consolidation, spatial, and declarative memory. I propose that stress-induced upregulation of C4 activity in the hippocampus promotes excessive synaptic pruning, contributing to specific deficits and hippocampal shrinkage seen in schizophrenia. Stress exposure during fetal development and adolescence likely acts through the proposed mechanisms to increase hippocampal C4 activity and subsequent schizophrenia risk. These mechanisms may reveal novel interactions between environmental and genetic risk factors in the etiology of schizophrenia through complement activation.
This hypothesis is supported by previous studies demonstrating that stress-induced elevation of glucocorticoids increases the transcription of C4. I propose that activated glucocorticoid receptors directly increase C4 protein expression as a transcription factor activator. Additionally, I propose that activated glucocorticoid receptors inhibit the expression of the transcription factor nuclear factor-light-chain-enhancer of activated B cells (NF-κB), thereby leading to decreased expression of the C4 inhibitor CUB and Sushi multiple domains 1 (CSMD1).
Glucocorticoid receptors and C4 are richly expressed in the hippocampus, a region critical in memory consolidation, spatial, and declarative memory. I propose that stress-induced upregulation of C4 activity in the hippocampus promotes excessive synaptic pruning, contributing to specific deficits and hippocampal shrinkage seen in schizophrenia. Stress exposure during fetal development and adolescence likely acts through the proposed mechanisms to increase hippocampal C4 activity and subsequent schizophrenia risk. These mechanisms may reveal novel interactions between environmental and genetic risk factors in the etiology of schizophrenia through complement activation.
ContributorsHoegh, Emily Marie (Author) / Orchinik, Miles (Thesis director) / Newbern, Jason (Committee member) / Talboom, Joshua (Committee member) / Department of Psychology (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05