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- Creator:
- Cohen, Randy W.
- Description:
- Animals, including insects, have the ability to self-select an optimal diet from a choice of two or more incomplete diets that lack an essential nutrient. This paper demonstrates that nymphs of the cockroach Rhyparobia madera also have this ability. The nymphs chose a protein:carbohydrate (P:C) ratio of approximately 25:75 when faced with a choice between one cube of protein (casein) and another of carbohydrate (sucrose). This self-selected ratio was shown to promote growth as well or better than other diets tested. When given a wide range of P:C choices, the R. madera nymphs consistently selected a P:C ratio of approximately 25:75, suggesting that they have the ability to diet-balance. Finally, injections of various serotonergic drugs into self-selecting nymphs influenced their choice of diets. Serotonin promoted a decrease in carbohydrate feeding, while injection of the antagonist ?-methyltryptophan caused the nymphs to overfeed on carbohydrate. The results suggest that serotonin may help alter the carbohydrate feeding response in cockroaches.
- Resource Type:
- Article
- Identifier:
- 0892-7553, 1572-8889
- Campus Tesim:
- Northridge
- Creator:
- Purvis, Tyler Chase
- Description:
- In recent decades, zebrafish have become a popular organism in neuroscience research. This is primarily because of the homogenous nature of what are known as reticulospinal neurons. These neurons, located in the hindbrain, control locomotive (e.g., swimming) and escape behaviors via descending axonal connections to lateral musculature. Dominating the reticulospinal neuron group are the Mauthner neurons. This pair of morphologically distinctive neurons is referred to as “command neurons” in the reticulospinal group. Recent studies involving antibody labeling reveal a distinctive clustering of serotonin (5-HT) associated proteins in the Mauthner dendritic regions. This would imply that 5-HT plays a direct role in the modulation of Mauthner neuron activity. In this study, we attempt to experimentally demonstrate a functional relationship between 5-HT and the Mauthner neuron through the administration of the SSRI fluoxetine and Ca²+ imaging techniques. Results indicate no significant change Ca²+ and latency of response. Interestingly, these data indicate a difference in responsiveness (i.e., firing or no firing) with the fluoxetine group showing an 8% increase. These data shed light upon the Mauthner neuron and 5-HT, as well as the possible considerations of future research
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Humboldt
- Department:
- Psychology
3. A larval zebrafish model of glucocorticoid-serotonin interactions in behavioral stress reactivity
- Creator:
- Griffiths, Brian B.
- Description:
- Neural mechanisms of stress are highly conserved across animals. Glucocorticoids (such as cortisol in humans) and serotonin are two neural signaling molecules that are essential to normal stress reactivity in many animals. These chemical signaling molecules are also believed to interact during stress responses. The details and functional consequences of that interaction are not well understood, but they have been proposed to influence the development of stress related disorders such as depression and anxiety in humans, as well as responses to antidepressant medications. This study used a mutant zebrafish strain, s357gr-/-, in which the glucocorticoid receptor is non-functional, to investigate the roles that glucocorticoids, serotonin, and their interactions play in behavioral stress reactivity. This mutant line has been proposed to be a model of behavioral stress disorders in humans. Mutant larvae showed larger locomotor responses and less habituation in an auditory-evoked startle test compared to wildtype sibling controls, despite having lower spontaneous locomotor activity levels. Mutants also had elevated whole cortisol levels. Fluoxetine was shown to increase spontaneous swimming activity in mutants as well as reduce locomotor activity in response to the auditory stimulus. These results provide partial support for the s357gr-/- zebrafish mutant as a model of human stress disorders in which the primary cause is a disruption in glucocorticoid signaling.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Humboldt
- Department:
- Psychology
- Creator:
- Wannigman, Kyle David
- Description:
- Hypnotherapy is an empirically supported, clinical intervention used in the treatment of a wide variety of mental, physical, and emotional dysfunctions. Hypnotizability is a stable and heritable personality trait. Individual differences in hypnotic susceptibility have been shown to correspond to hypnotherapeutic success. Increasingly, gene variants have been linked to facets of personality as well as their related psychological and physiological disorders. These variants are used as predictors of responses to medical treatments including drugs, psychotherapy, and placebo effects. These studies support hypotheses relating specific gene variants to differences in hypnotizability. This study investigated two allele variants and their associations to susceptibility: the serotonin transporter gene linked polymorphic region 5HTTLPR and the single nucleotide polymorphism of the catechol-O-methyltransferase at Codon 158. A secondary goal was to assess the validity of the Tellegen Absorption Scale (TAS) by comparing scores to actual hypnosis susceptibility. Hypnotic susceptibility was measured using a standardized group induction method – the Harvard Group Scale for Hypnotic Susceptibility (HGSHS-A). Hypnotizability, TAS scores, COMT genotype, and SERT genotype, was measured in 253 participants. There were no main effects of either gene variant on hypnotic susceptibility and no interactions effects between these genes. TAS scores were not significantly correlated with scores on the HGSHS-A, suggesting that TAS is not a valid measure of the hypnotizability construct. These negative results are consistent with other recently published studies. A review of the literature suggests that commonly used testing methods for hypnotic susceptibility may conflate multiple constructs and decrease the probability of detecting susceptibility correlates.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Humboldt
- Department:
- Psychology