Browsing by Subject "Serotonin"
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Item Acclimation of Holstein Calves to Transit Stress: The Integration of Endocrine, Immune, and Behavior Systems(2012-10-19) Adams, AmberLittle is known about the adaptation of livestock to repeated transport. This study determined how repeated transport affected calf feed intake, plasma cortisol (CORT), post-transport behavior, and the expression of immune-related genes. Thirty-six 4-month-old Holstein steer calves were housed in groups of six with each group randomly assigned to either transport (T) or control (C) treatments. The T calves were hauled for 6 h in a 7.3 m x 2.4 m goose-neck trailer, at an average density of 0.87 m2/calf, every 7 d for five consecutive weeks. Individual daily intake was determined using Calan gate feeders. Blood samples were obtained in the trailer or home pen via jugular venipuncture before loading, and after 2, 4, and 6 h of transport. Samples were analyzed for CORT, serotonin, tryptophan, and the gene expression of interleukin-4 (IL-4), interleukin-6 (IL-6), chemokine (C-X-C motif) receptor 2, interleukin-12, toll-like receptor-4, toll-like receptor-2, and 5-hydroxytryptamine receptor 2A in leukocytes. Behavior was recorded for transported calves at 5-min intervals for 1 h after return to their home pens. The C calves had a higher feed intake than T calves overall (P = 0.01), on the day of transport (P = 0.007), and the day after transport (P = 0.02). Pre-transport CORT concentrations did not differ by treatment (P = 0.77) or trial (P = 0.32). However, the T calves had higher response CORT concentrations than C calves during Transport 3 (P = 0.006), Transport 4 (P = 0.001) and Transport 5 (P = 0.02). The T calves had the highest response CORT concentrations after 2 h of transport and the lowest response CORT concentrations after 6 h of transport (P < 0.0001). Treatment did not affect gene expression in leukocytes, however, the expression of IL-4 (P = 0.01) and IL-6 (P = 0.05) was significantly lower after 2 h of transport than any other sampling times. These results suggest conflicting conclusions on whether the calves started to acclimate after being transported five times. However, CORT and gene expression differences occurred in response to the blood sampling regimen, which may provide insight to how calves acclimate during prolonged stress.Item Effects of auditory and thermal stimuli on 3,4- methylenedioxymethamphetamine (MDMA)-induced neurochemical and behavioral responses(2009-12) Feduccia, Allison Anne; Duvauchelle, Christine L.The amphetamine derivative, 3,4-methylenedioxymethamphetamine (MDMA), is a popular drug often taken by young adults at dance clubs or rave parties. Laser light shows, fast-paced electronic music, and hot crowded dance floors are characteristic of these events, and Ecstasy users report that the acute effects of the drug are potentiated by these stimulatory conditions. However, it remains largely unknown how environmental stimuli impact the neurochemical and physiological effects of MDMA. The aim of the first study presented in this dissertation was to investigate how auditory stimuli (music, white noise, and no additional sound) influence MDMA conditioned place preference (CPP), self-administration, and nucleus accumbens (NAcc) dopamine (DA) and serotonin (5-HT) responses. Findings revealed a significant CPP for animals exposed to white noise during MDMA conditioning trials. After self-administration of MDMA (1.5 mg/kg), NAcc DA and 5-HT were highest in rats exposed to music during the test session. The second study aimed to investigate the effects of ambient temperature (23°or 32°C) on long-term MDMA self-administration and neurochemical responses. Results indicated no difference in self-administration or locomotor activity rates for the high versus room temperature groups across sessions. However, MDMA (3.0 mg/kg) administered in high ambient temperature resulted in significantly greater NAcc serotonin release compared to when taken at room temperature, but no differences in dopamine response was determined between the two conditions. Overall, these results indicate that auditory and thermal stimuli can effect MDMA-induced behavioral and neurochemical responses. The last aim tested a novel apparatus and method for use in animal models of drug reinforcement. By combining traditional CPP and self-administration procedures, this approach provided more informative data and circumvented some inherent drawbacks of each method alone. In addition to confirming the ability to produce drug conditioned place preferences after short- and long-term experiments, the long-term version of the procedure revealed a significant positive relationship between lever response rate and CPP magnitude. Therefore, this experimental design can be used to identify subgroups of rats that may vary in sensitivity to drug motivational effects. Further study of these populations may be useful in the development of behavioral and pharmacological therapies for drug addiction.Item Electrophysiological analysis of cerebellar serotonergic mechanisms in thiamine deficiency(Texas Tech University, 1983-08) Lee, Rong-shengNot availableItem Expression of the human 5-HT3A receptor using the baculovirus- and Epstein-Barr virus (EBV)-based expression systems(Texas Tech University, 2000-08) Liu, MinghuaDue to the scarcity of 5-HT3A receptors in native tissue, it is extremely difficult to isolate sufficient quantities of protein to perform structural and biophysical studies on them. High-level heterologous expression systems provide a means of overcoming this limitation. The cDNA ofthe human 5-HT3A receptor with a hexa-hisfidine at its Cterminus was constructed with a PCR cloning strategy and was confirmed with dideoxy sequencing. The function ofthe recombinant 5-HT3A receptor was examined using the Xenopus laevis oocyte expression system and two-electrode voltage-clamp electrophysiological recordings. Application of serotonin to recombinant receptors elicited inward sodium currents. No significant difference was revealed in the EC50S of serotonin in wild-type and 5-HT3A-His6 receptors. The cDNA for the human 5-HT3AHis6 receptor was subcloned into a baculovirus transfer plasmid and expressed in baculovirus-infected Sf9 insect cells. The expression ofthe human 5-HT3A-His6 receptor was assessed with both Western blot analysis and nickel affinity purification. In addition, saturation-binding experiments were carried out with crude membranes from baculovirus-infected insect cells and using affinity-purified receptors with the 5-HT3R antagonist [^H] GR65630. The KItem Familiar Food-Induced Feeding Activation in C. Elegans(2011-08-26T17:35:11Z) Song, Bo-mi; Avery, LeonThe growing epidemic of obesity and eating disorders demands the study of regulatory mechanisms of food intake. Studying mutants whose food intake is altered under various conditions has greatly advanced our understanding of the mechanism. However, it is still largely unknown by which mechanisms perception of food activates food intake. The simple anatomy, genetic tractability, and well-characterized and quantifiable feeding behavior and evolutionary conservation of feeding regulators make C. elegans an attractive model system for the study. Food intake in C. elegans requires two muscle motions, pharyngeal pumping and isthmus peristalsis, and the frequencies of the two feeding motions dramatically increase in response to food as in other organisms. I attempted to understand the mechanism underlying food-induced feeding activation by studying the mechanism and the physiological context of action of serotonin, an endogenous activator of pharyngeal pumping. Here I show that like food, serotonin increases overall feeding by activating both feeding motions. Serotonin activates the two feeding motions by activating two distinct neural pathways. A 5-HT7 receptor activated the two motions mainly by acting in the two distinct pharyngeal motor neurons that are essential for food-induced feeding activation. Moreover, the results support that the serotonin receptor activated the two distinct neurons mainly by activating two distinct downstream G protein signaling pathways. Despite the separate regulation, isthmus peristalsis was coupled to the preceding pharyngeal pump. The separate regulation with coupling of the two feeding motions may have evolved to support efficient feeding by allowing control of the ratio of the frequencies of the two muscle motions according to density of food and by preventing futile isthmus peristalsis. Then, which aspect of food triggers the serotonin signal that increases food intake? I found that recognition of familiar food selectively triggers the serotonin signal. Worms selectively consume particular bacteria more actively after experience and the behavioral plasticity requires serotonin signaling. By dissecting the mechanism, I found that recognition of familiar food triggers serotonin release from a pair of chemosensory neurons. The released serotonin acts as an endocrine signal to increase pharyngeal pumping rate by activating the pharyngeal motor neuron that directly triggers pharyngeal pumping. The results suggest that worms form a memory of previously experienced food and that the memory controls food intake. Consistently, the familiar-food induced feeding was strongly dependent on duration of exposure to food to learn but not developmental timing of exposure or nutritional status. Furthermore, worms could remember the previously experienced food at least for several hours. My study provides insight into how feeding organ operates to increase food intake in response to food and how a particular aspect of food controls the process to increase food intake in C. elegans. Studying familiar food-induced feeding activation may help us understand the mechanisms underlying perception of different food and encoding, retention and retrieval of the memory of familiar food.Item Molecular parsimony underlying behavioral plasticity(2008-08) Dias, Brian George, 1980-; Crews, DavidThe brain is inherently bisexual, differentiating during development so that in adulthood, males mount receptive females. Yet, vestiges of this bisexuality persist in adults, with heterotypical behaviors (females mounting and males being receptive) observed in some species. Consequently, differences in sexual behavior between the sexes, and between individuals of the same sex, are reflective of the predisposition and degree to which these behaviors are exhibited. How one behavior is facilitated and its complement simultaneously suppressed during a reproductive encounter suggests that behavioral expression is gated in some manner. Because male and female vertebrates typically display behavior characteristic of their own sex, simultaneous study of neural circuits gating homotypical and heterotypical behaviors in conventional animal models has received scant attention. The whiptail lizard species, Cnemidophorus uniparens, comprises individuals that are genetically and hormonally female, and that naturally display both types of behavior. Using High Pressure Liquid Chromatography (HPLC), immunocytochemistry, in situ hybridization, intracranial surgeries, as well as pharmacological and behavioral analyses, I report that serotonin levels, and signaling via distinct serotonergic receptors at behaviorally relevant brain nuclei might allow the system to switch between either behavioral repertoire. The use of the same molecule to mediate the reciprocal inhibition of complementary behavioral repertories within the same sex is evidence of a phenomenon of molecular parsimony underlying a striking form of behavioral plasticity. This dissertation also illustrates that sexually differentiated traits such as male and female-typical sexual behaviors are sculpted by neurochemical signaling at neural substrates present in both sexes.Item Oxytocin and serotonin and their roles in pre-pubertal social development in syrian golden hamsters(2014-12) Edgar, Emma Marie; Delville, YvonThe pre-pubertal infancy stage of development is marked by numerous neurological and behavioral changes in Syrian Golden Hamsters. One of the most notable changes during this period is the onset of social behaviors including social playfighting. Social playfighting is initiated approximately two weeks postpartum and is completely abolished by mid-puberty. The neural mechanisms that underlie this behavioral change are not well understood, but previous research has identified both oxytocin (OT) and serotonin (5-HT) as possible regulators of this behavior. In the present study, immunohistochemical techniques were used to evaluate changing levels of OT and serotonin 5-HT in the developing brain with the hypothesis that both OT and 5-HT levels would increase and decrease simultaneously with the onset and decline of social playfighting. Additionally, it was predicted that injections of a 5-HT3 receptor agonist, m-Chlorophenylbiguanide hydrochloride (CBG), into hamster in late infancy would reinstated social playfighting behaviors. Contrary to the hypothesis, OT was found to continually increase in the fornix, lateral hypothalamus, nucleus accumbens, medial preoptic area, and anterior hypothalamus, while 5-HT continually decreased in the lateral septal nucleus and medial preoptic area. CBG injections did not reinstate social playfighting behaviors, however a large stress effect was observed, potentially masking any other effect. Analysis of OT and 5-HT receptors during this developmental stage is necessary for a better understanding of this neural mechanism. Further research into this topic may have important implications for animal models of autism spectrum disorders.