It is well established that estrogens suppress feeding primarily by reducing meal size, and that this is partly mediated by enhancement of the response to satiation signals. Glucagon-like peptide 1 (GLP-1) acts on receptor populations both peripherally and centrally to affect food intake. Most research on the feeding effects of GLP-1 has used exclusively male subjects, and little is known about the effects of GLP-1 in females. We hypothesized that modulation of the central GLP-1 system is one of the mechanisms underlying the effects of estrogens on ingestive behavior. More specifically, we hypothesized that estradiol, a common estrogen, enhances the anorexic response to central GLP-1. To investigate this possibility, bilaterally ovariectomized female rats were placed on a cyclic regimen of either 2 μg β-estradiol-3-benzoate or oil vehicle and implanted with unilateral cannulas targeting the lateral ventricle. We assessed the food intake effects of 0, 1, or 10 μg doses of GLP-1 in oil- or EB-treated rats administered 30 min prior to dark onset on the day following hormone treatment. GLP-1 treatment significantly suppressed food intake in EB-treated rats at both doses compared to vehicle, whereas only the 10 μg dose was effective in oil-treated rats. We then examined whether estrogen status alters the neuronal response to GLP-1 by measuring GLP-1-induced c-Fos expression in several feeding-relevant brain areas. While GLP-1 significantly increased c-Fos expression, there were no significant differences between hormone treatment groups in the brain areas examined. These experiments suggest that modulation of the central GLP-1 system may be one of the mechanisms by which estrogens suppress food intake and support the need for further examination of this effect. / A Thesis submitted to the Department of Psychology in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester 2015. / October 29, 2015. / c-Fos, estradiol, food intake, GLP-1, glucagon-like peptide 1, pharmacology / Includes bibliographical references. / Diana L. Williams, Professor Directing Thesis; Lisa A. Eckel, Committee Member; Pamela K. Keel, Committee Member.

The taste system enables the detection and discrimination of potential nutrient sources necessary for maintaining essential life processes. Nutrients bind with taste receptors in the oral cavity that convert the food-derived signal into neural activity interpretable by the brain. The four independent, canonical taste qualities are "sweet", "salty", "sour", and "bitter" with additional proposed basic tastes, such as "umami", "polysaccharide", and "fat" taste, garnering support in the literature. A given taste quality is elicited by nutrient compounds that share chemical properties. The proposed qualities of interest here were "umami" and "polysaccharide" taste. Prior in vitro and in vivo studies suggest that the taste receptor mechanisms responsible for mediating "sweet" taste, elicited by sugars and sweeteners, and "umami" taste, elicited by L-glutamate, in mammals are heterodimers of the Taste Receptor Type 1 (T1R) proteins—T1R2+T1R3 and T1R1+T1R3, respectively. However, whether the T1R1+T1R3 heterodimer is the sole mediator of "umami" taste is not without controversy; other mechanisms have been proposed. Further disputes relate to the classification of "umami" as an independent taste quality. Whereas a portion of the literature implicates "umami" as a unique taste sensation, evidence suggests it represents a mere combination of "salty" and "sweet" taste. The experiments here (Chapters 2-6) combined psychophysical methodology with genetic knockout models to address the following: 1) Are the individual T1R proteins—T1R1, T1R2, and T1R3—necessary for maintaining sensitivity to "umami" stimuli? 2) Given the proposed commonalities between "umami" and "sweet" taste, is the T1R2+T1R3 involved in transducing the L-glutamate signal? 3) How is sensitivity to other non-"umami"-tasting amino acid stimuli affected upon deletion of one or more T1R proteins? The taste detection of the prototypical "umami" stimulus, monosodium glutamate (MSG), in wild-type (WT) controls, and T1R1, T1R2, T1R3, and T1R2+T1R3 knockout (KO) mice was severely impaired if not eliminated when the taste signal from the sodium component was minimized by the epithelial sodium channel (ENaC) blocker amiloride. Only when inosine monophosphate (IMP), a known potentiator of the L-glutamate taste signal, was prepared with the MSG and amiloride mixture were WT and T1R2 KO mice able to detect the compound stimulus due, in part, to the taste of IMP. In contrast, mice lacking T1R1 or T1R3 were incapable of detecting IMP alone, but showed sensitivity to at least the higher concentrations of MSG (+amiloride) when IMP was present. Similarly, T1R2+T1R3 KO mice showed significant sensitivity loss to the purportedly "sweet-like" achiral amino acid glycine. However, the sensitivity of T1R1 KO mice to L-lysine was unimpaired. Collectively, these data demonstrate the necessity, but not exclusivity, of the T1R subunits in the taste transduction of some amino acids such as MSG (in the presence of IMP) and glycine. The partial competence observed in some of the mice lacking the T1R1 or T1R3 subunit suggests the presence and activity of another receptor independent of the T1R1+T1R3 heterodimer—perhaps a novel protein or T1R homodimer. Furthermore, unimpaired sensitivity to L-lysine in the T1R1 KO mice suggests that some L-amino acids can be detected through T1R1+T1R3-independent mechanisms without sensitivity loss. Polysaccharides, specifically maltodextrins, such as Maltrin and Polycose, are composed of glucose polymer mixtures of varying glucose chain lengths. Although glucose and other sugars activate the T1R2+T1R3 heterodimer, maltodextrins are suggested to potentially bind with a different receptor leading to the generation of a qualitative taste perception distinguishable from that of sweeteners. Recent evidence supporting this hypothesis derives from T1R2 or T1R3 KO mice. While these KO mice display relatively normal responses to maltodextrins the slight impairments in behavioral responsivity raise the possibility that T1R homodimers might contribute to polysaccharide taste transduction. Therefore, experiments incorporating psychophysical methodology and mice lacking both T1R subunits of the sweet taste receptor (Chapter 6) were conducted to address the following questions: 1) Is the T1R2+T1R3 heterodimer necessary for maltodextrin taste detection? 2) Do maltodextrins and sweeteners possess discriminable taste characteristics? Most T1R2+T1R3 KO mice displayed similar sensitivity to Polycose as WT mice. However, some were only sensitive to the higher Polycose concentrations, implicating potential allelic variation in the polysaccharide taste receptor. Concentrated polysaccharide and sweetener solutions are characteristically viscous, at least at the higher concentrations, and this oral somatosensory stimulus feature may serve as a cue in this taste detection task. Therefore, viscosity-matched Maltrin and sucrose concentrations were presented to KO and WT mice in a 2-tastant operant discrimination procedure. Both WT and KO mice competently discriminated Maltrin from sucrose. However, performance in WT mice was likely driven by the different taste percepts of the two stimuli, while KO mice likely relied on the taste cue from Maltrin as opposed to sucrose. To my knowledge, these results represent the first demonstration that maltodextrin is qualitatively distinguishable from sucrose in an explicit taste discrimination task, and, coupled with the detection data, implicate that distinct dedicated taste pathways from the periphery to central circuits are mediating polysaccharide and sugar taste. / A Dissertation submitted to the Department of Psychology in partial fulfillment of the Doctor of Philosophy. / Fall Semester 2015. / September 11, 2015. / knock-out, psychophysics, taste / Includes bibliographical references. / Alan C. Spector, Professor Directing Dissertation; Jasminka Ilich-Ernst, University Representative; Robert Contreras, Committee Member; Michael Meredith, Committee Member; Jeanette Taylor, Committee Member.

A cross-cultural investigation of a male-male competition hypothesis regarding the evolution of male homosexual behavior was conducted using the Human Relations Area Files Probability Sample. Nine predictions pertaining to the incidence of homosexual behavior within cultures and consequences of the male-male competition hypothesis were tested. In addition, statistical control procedures were incorporated so as to evaluate the predicted relationships while minimizing bias. Seven of the nine predicted relationships received at least tentative support from the analyses, with two relationships receiving unqualified support. Of particular importance was the strong, positive correlation between the level of male homosexual behavior within cultures and the degree of polygyny within those cultures. Two predictions based on other proposed models for the evolution of homosexual behavior (kin-selection and bonding) resulted in non-significant world-wide correlations. Thus, it is suggested that factors which universally contribute to variability in the intensity of male-male competition may produce differences in the likelihood of the expression of homosexual behavior, while the particular advantages which may accrue to the individuals involved in this behavior have yet to be identified empirically. These advantages may be specific to certain cultural and personal situations rather than being universal. / Source: Dissertation Abstracts International, Volume: 44-11, Section: B, page: 3566. / Thesis (Ph.D.)--The Florida State University, 1983.

Three groups of laboratory rats were presented with water, laboratory chow, and a sugar solution for 23 hours and their eating and drinking patterns were quantified. Each group received either a glucose, fructose or maltose solution. The concentration of the sugar solution was systematically increased (4%, 8%, 16%, 32%) with a single concentration being presented to rats in four day blocks. For all three sugars, total intake (ml) of sugar solution increased with concentration, reaching a peak at 8% and then decreased with further rises in concentration. Calories consumed from sugar monotonically increased with concentration, reaching an asymptote at 8% for both glucose and maltose and at 16% for fructose. As calories consumed from sugar increased with rising concentration, chow intake decreased. The decrease in chow intake was due primarily to a reduction in feeding bout frequency. As the concentration of sugar increased, the day to night ratio of sugar intake approached unity. This was attributed to an increase in the incentive value of the sugar solution, provoking ingestion during the daytime, with postingestional inhibition limiting nighttime intake. Fluid bout volume increased with sugar concentration up to 8% and then either remained the same or dropped when the concentration was raised from 8% to 16% depending on the sugar. All groups decreased their fluid bout volume when the concentration was raised from 16% to 32%. These data suggest that caloric density is an important factor in the limitation of bout volume. Since caloric intake within a sugar drinking bout progressively increased with each rise in sugar concentration, the asymptotic portion of the curve describing calories consumed from sugar was attributable to alterations of drinking bout frequency and not drinking bout size. This finding also suggests that caloric load is not the sole factor / responsible for the limitation of bout volume. Bout drinking rate (ml/min) monotonically increased with concentration reaching an asymptote at 8% for glucose and at 16% for fructose and maltose. This finding supports the claim that the incentive value of sugar solutions does not decrease with high sugar concentrations. / Source: Dissertation Abstracts International, Volume: 45-08, Section: B, page: 2730. / Thesis (Ph.D.)--The Florida State University, 1984.

Visual masking was measured in two human psychophysical experiments which showed that the contrast threshold to a grating test stimulus and the increment threshold to a spatially homogeneous (flash) test stimulus were elevated when they were preceded, respectively, by a grating or flash masking stimulus over a range of stimulus onset asynchronies (SOAs) from 55 to 200 milliseconds. The amplitude of the visual evoked cortical potential (VECP) to a test stimulus was then measured in anesthetized, paralyzed cats under the stimulus conditions used in the psychophysical experiments. The amplitude of the VECP was reduced when the test stimulus was presented after the masking stimulus at SOAs shown to produce masking in the psychophysical experiments. It was concluded that the reduction in VECP amplitude could be used as a physiological measure of visual masking and experiments were conducted to identify the properties and neural locus of the masking effects. / Visual masking was produced by both monoptically and dichoptically presented gratings and flashes. Masking produced dichoptically must be attributed to cortical mechanisms. However, the degree of masking was significantly weaker for dichoptically presented stimuli, suggesting that masking produced monoptically was both peripheral and central in origin. / Masking produced by monoptically presented gratings was greatest when the contours of the masking and test stimuli had the same spatial phase and orientation and was reduced by half when the orientation of the contours differed 6(DEGREES) to 15(DEGREES). A cortical neural locus for orientation-selective masking was demonstrated by simultaneous recordings of evoked potentials in the optic tract and visual cortex, which showed the degree of masking measured in the optic tract was independent of test stimulus orientation. / The findings support an integration theory of masking which posits that masking results when the masking and test stimuli evoke responses in the same neural elements and produce a degradation of the response to the test stimulus. Masking and test stimuli with contours differing in orientation would excite separate populations of orientation-selective cortical neurons and thereby produce little masking. / Source: Dissertation Abstracts International, Volume: 44-02, Section: B, page: 0643. / Thesis (Ph.D.)--The Florida State University, 1983.

Electric taste may be described as the perception of a taste produced by passing a small current through the tongue. These studies were undertaken to gain some insight into its mechanism on both a neurophysiological and biophysical basis by recording electrophysiologically from the chorda tympani nerve of the rat in response to both electrical and chemical stimulations of the tongue. / The response profiles of chemical and electrical stimulations saturated at the same maximum response for each individual salt tested (LiCl, NaCl, KCl, and CaCl(,2)) indicating an ion specificity for electric taste. This observation supports the idea of iontophoresis of ions at these curent densities ( 300 microamps/sq. cm.). If the taste cells of the tongue were inactivated with either Iodoacetic acid or N - ethyl maleimide or removed with collagenase, then responses from the chorda tympani could only be obtained at these higher current densities. / A mechanism was proposed for electrical stimulations which accounts for the responses as a result of ion accumulation around the state receptor membranes. The membrane, acting as an anion exchanger, selectively accumulates cations to anodal current countering the charge with anions from the cell's interior. The magnitude of this accumulation is proposed to be a balance of ions being accumulated by the current and diffusing away, down their concentration gradient, into the bulk solution. / Source: Dissertation Abstracts International, Volume: 44-02, Section: B, page: 0641. / Thesis (Ph.D.)--The Florida State University, 1983.

Background: Social exclusion is a robust correlate of suicidal ideation and behavior. However, there is little research examining the biological factors contributing to the link between social exclusion and suicide risk. Prior research has indicated that oxytocin, an important modulating neuropeptide in the regulation of social interactions, protects against the negative effects of social exclusion by motivating social behavior in excluded individuals. In non-psychiatric controls, oxytocin levels and desires to affiliate with others increase in response to feelings of loneliness and social exclusion; however, in individuals with psychiatric disorders that are associated with serious suicide-related symptoms, oxytocin levels decrease in response to social exclusion. This suggests that dysregulated oxytocin functioning may be a correlate of suicidal behavior among socially excluded, at-risk individuals. However, crucially, no studies have examined this potential association. Aims: This study examined whether individuals with and without a history of suicide attempts differ in their oxytocin levels and desires to affiliate with others at baseline and following social exclusion. Methods: Young adults (N = 100) with and without prior attempts completed Cyberball, a computerized, social exclusion paradigm. Prior to and approximately 10 minutes after Cyberball, blood samples and levels of self-reported desires to affiliate with others, thwarted belongingness and perceived burdensomeness were obtained. Data were analyzed using one-way MANOVAs and two-way mixed design ANCOVAs. Results: No group differences emerged at baseline. Although no main effects emerged, a significant group by time interaction effect emerged such that among suicide attempters, desires to affiliate and oxytocin levels significantly decreased following social exclusion. Among depressed and healthy controls, desires to affiliate and oxytocin levels increased following exclusion. There were no significant changes in thwarted belongingness and perceived burdensomeness across groups following exclusion. Conclusions: Overall, our findings suggest that dysregulated oxytocin levels in response to social exclusion may be a correlate of suicide risk. / A Dissertation submitted to the Department of Psychology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2017. / February 22, 2017. / interpersonal theory of suicide, oxytocin, perceived burdensomeness, social exclusion, suicide attempt, thwarted belongingness / Includes bibliographical references. / Thomas E. Joiner, Professor Directing Dissertation; David Kirby, University Representative; Elizabeth A. D. Hammock, Committee Member; Wen Li, Committee Member; Jesse Cougle, Committee Member.

Albino rats were maintained in varying illuminances of cyclic light (12L:12D) from birth through 15 weeks. Upon sacrifice, several retinal parameters were tested for differences between animals raised in one illuminance and another. These parameters were: (1) dark-adapted whole retina rhodopsin level, (2) steady-state whole retina rhodopsin level, (3) rod outer segment length throughout the retina, (4) photoreceptor cell density throughout the retina, (5) in situ rhodopsin absorbance throughout the retina, and (6) rhodopsin regeneration rate in vivo. The range of illuminances in the animals' habitats was 3 lux to 800 lux. / Results proved that albino rats were able to change a combination of the above parameters in order to adapt to the illuminance of their environment. Specifically, there was four times more rhodopsin in the whole retina extract of dark-adapted animals which were raised in 3 lux than those raised in 400 lux. Changes in the transverse absorbance, determined by microspectrophotometry, and the length of outer segments accounted for this difference. The microspectrophotometry was carried out on fixed and frozen sections of retina. The transverse absorbance measures were the absorbance in small volumes of the outer segment layer, and took into account both the density of cells and the density of pigment within cells. The change in dark-adapted rhodopsin content, coupled with the ability to alter their pigment regeneration rate, allowed the animals to control the amount of pigment in their retinas at steady-state bleach. By altering this amount, the rats controlled the number of photons their retinas caught each day with great accuracy. Animals raised in cyclic illuminances ranging from 3 to 400 lux caught a statistically equal number of photons (2.03 (+OR-) 0.2 x 10('16)) during the light period. / This study detailed a continuum of adaptation over a wide range of cyclic illuminances and revealed a retinal plasticity previously unknown in vertebrates. The possible evolutionary significance of this plasticity was briefly considered. / Source: Dissertation Abstracts International, Volume: 45-09, Section: B, page: 3109. / Thesis (Ph.D.)--The Florida State University, 1984.

A technique was developed for obtaining odor psychophysical data from pigeons. Each pigeon was phyically restrained so that its beak was held within the stimulus air steam and it was required to make one response in the presence of odor and another in the presence of clean air. Absolute thresholds to amyl acetate were between 10('-3.4) and 10('-3.6) of vapor saturation for each of three pigeons tested. / Following the determination of absolute threshold the olfactory nerves were bilaterally sectioned in each animal, and each was tested after this operation in an attempt to monitor the return of olfactory sensitivity due to reconstitution of the olfactory nerve. One pigeon regained preoperative levels of sensitivity within 20 days. Another pigeon showed nearly complete recovery 10 weeks after sectioning, after which its threshold increased by approximately .7 log unit and remained stable at this level. A third pigeon failed to exhibit any postoperative odor-air discrimination during 99 days of testing. / These results demonstrate that normal behavioral sensitivity to an odorant is possible with reconstituted nerves and that the recovery process following nerve sectioning may occur in less than three weeks. Possible explanations are given for the high degree of variability found across subjects. This study represents an initial step toward quantifying the relationship between the degree replacement of olfactory axons with reconstitution and the degree of recovery of specific olfactory capacities. / Source: Dissertation Abstracts International, Volume: 41-05, Section: B, page: 1967. / Thesis (Ph.D.)--The Florida State University, 1980.

Source: Dissertation Abstracts International, Volume: 41-01, Section: B, page: 0401. / Thesis (Ph.D.)--The Florida State University, 1979.