Stimulation of dopamine D2S receptor introduced in Balb/c-3T3 cells induces Galphai3-dependent transformation. Galphai3 interacts with DED2-containing protein, TNFAIP8, in yeast mating and in FLAG-TNFAIP8 transfected Balb/c-3T3 cells. TNFAIP8 inhibits caspase-8 activity and is elevated in certain cancers as well as in metastatic, radiation resistant, chemo-resistant and angiogenic tumours. This study looks at Galphai3 activation of TNFAIP8 leading to the inhibition of TNFalpha-induced cell death in Balb/c-3T3 cells coexpressing D2S and either TNFAIP8 over-expression or TNFAIP8 antisense-knockdown with assays for foci formation, cell death and executioner caspase activation. The data showed D2S increases basal foci formation; this is blocked in TNFAIP8 antisense cells. D2S activation further increases foci formation; also completely blocked in TNFAIP8 antisense cells. D2S activation reduces cell death except in TNFAIP8 antisense cells. D2S activation reduces caspase-active cells. These results show that D2S mediated inhibition of caspase activity and death resulting in transformation is dependent on TNFAIP8.

This thesis explores thyroid hormone (TH) effects on adult neuroendocrine brain and pituitary in goldfish (Carassius auratus) to address the hypothesis that THs regulate the reproductive neuroendocrine axis through effects on gamma-aminobutyric acid (GABA), a neurotransmitter that stimulates gonadotropin release in fish. The experimental approach was to increase circulating levels of the TH 3,5,3'-triiodothyronine (T3) in goldfish through waterborne exposures, and measure effects on gene expression, enzyme activity and hormone levels in comparison to controls. In sexually regressed males, T3 exposure decreased gene expression of GABA-synthetic and degradative enzymes (glutamic acid decarboxylase and GABA-transaminase, respectively) in telencephalon in a time- and dose-dependent manner but not in hypothalamus. GABA-transaminase activity was not affected by this T3 challenge. In sexually mature males and females, T3 treatment resulted in increased follicle stimulating hormone beta subunit expression in pituitary in females only, and had no effect on luteinizing hormone (LH) beta subunit expression or circulating LH levels in eider sex. Further experiments with GABA agonists indicated that T3 exposure had no effect on GABA-mediated LH release. TH receptor expression was affected in a tissue-specific manner by T3 exposure, appearing to be autoregulated in pituitary, but unaffected in neuroendocrine brain regions. TH deiodinase expression in brain and pituitary and thyroid stimulating hormone beta subunit expression in pituitary was affected in a manner reflective of negative feedback by T3 to reduce T3 levels in tissues and in circulation to a set-point. Gene expression profiling with cDNA microarrays indicated a large-scale decrease in gene expression in adult male goldfish telencephalon in response to T3. This included genes encoding proteins with functions central to general metabolic activity including mRNA splicing and proteasomal protein turnover, as well as neuroendocrine signalling relevant to reproduction and neurogenesis. In conclusion, THs have the potential to regulate the reproductive neuroendocrine axis through minor effects on GABA function in neuroendocrine brain and sex-dependent effects on glycoprotein hormone subunit gene expression, except for LH beta, in pituitary. Moreover, gene expression in adult teleost brain is responsive to TH, which is critical to understanding the potential for TH regulation of the reproductive neuroendocrine axis in teleosts.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 71-02, Section: B, page: . Adviser: Graeme W. Davis.

The neurotransmitter gamma-aminobutyric acid (GABA) stimulates the release of luteinizing hormone (LH) by enhancing gonadotropin-releasing hormone (GnRH) release in the goldfish, Carassius auratus. Activin A is another protein that stimulates the release of LH. Activin A also stimulates the release of GnRH from the rat hypothalamus, but this effect has never been shown in fish. Using real-time RT-PCR, we have shown that an injection of baclofen, a GABAB receptor agonist, into sexually mature goldfish stimulates the expression of activin betaA subunits in the telencephalon and sGnRH in the hypothalamus. Baclofen also inhibits the expression of that activin receptor IIB and IB in the hypothalamus. Immunocytochemical studies show that activin betaA subunits and activin receptors are localised in the olfactory bulb, telencephalon, thalamus, hypothalamus and optic tectum. Activin receptors are colocalised with GnRH fibres in the hypothalamus. This study has provided further insight into the role of activin as a neuroendocrine factor controlling reproduction in the goldfish brain.

Dopamine (DA) is the single most potent inhibitor of luteinizing hormone (LH) release from the fish pituitary and is fundamental to the neuroendocrine control of reproduction in vertebrates. It exerts its functions through DA D1- and D2-specific postsynaptic receptors. In order for DA to be such a potent inhibitor of reproduction, I hypothesized that DA must inhibit multiple LH-stimulatory systems in the brain. I provide the first evidence that a specific DA receptor, the D2 receptor, is alternatively spliced in fish and discuss its significance in terms of the inhibitory tone of DA. A wide-scale assessment of the genes and proteins that are under the regulatory control of DAergic action is provided and begins to elucidate mechanistic pathways that DA may be modulating and showed that D1- and D2-receptor specific agonists modulate different biochemical pathways. It is then shown that DA, acting through the D1 receptor, may be modulating the effects of another neurotransmitter, glutamate, through AMPA-type receptors. Blockage of the D1 receptor resulted in a rapid and pronounced increase of activin betaa transcription and subsequent stimulation with AMPA resulted in a significant increase in isotocin and chicken-type gonadotropin-releasing hormone, concurrently with increased circulating LH levels. The hypothalamic expression of a neuronal stem cell marker, DA cell markers and developmental factors are significantly increased in the days following injection with a specific DA neurotoxin. This provides evidence for DA neuron regeneration in the adult hypothalamus, and is indicative of an intrinsic regenerative capacity of the principle hypophysiotropic LH-inhibitory system for dynamic recovery and maintenance of function after injury. Comprehensive meta-analysis of microarray data identified 268 ESTs that are very likely to be transcriptionally-regulated by DA, indicating the major influence of DA on hypothalamic function. The hypothesis that industrial pollution (pulp and paper mill effluents) inhibits reproduction in the fathead minnow was tested by determining effects on the hypothalamic gene expression. This thesis (1) characterizes the role of DA in neuroendocrine function in fish; (2) identifies a novel mechanism of LH release mediated through DA, and; (3) demonstrates an ecologically-relevant and industrial application of the findings of this thesis.

Systems level consolidation is the process by which memories that are initially dependent on one memory system for recall become independent of that system over time. Current theories of consolidation propose that some, but not all, forms of memory initially dependent on the hippocampus may be consolidated in the neocortex. One rodent memory model that undergoes consolidation outside of the hippocampus is social transmission of food preferences (STFP). Of interest, there has been some evidence to indicate that the orbitofrontal cortex (OFC) may be involved in the remote recall of socially transmitted food preferences. The experiments conducted within this dissertation test specific hypotheses about the contributions of the hippocampus and OFC to learning and memory for STFP. Levels of transcription factors involved in consolidation were measured following acquisition, recent recall, and remote recall across several brain regions implicated in STFP memory. These findings indicate a time-limited role for the hippocampus and an increasing contribution of the OFC. In addition, excitotoxic lesions of the hippocampus and orbitofrontal cortex were made to test the necessity of these regions in STFP acquisition, consolidation, and recall. Consistent with previous reports, damage to the hippocampus impaired recent recall but spared remote recall and acquisition. Damage to the OFC had no effect on acquisition or recall. The main conclusion from this work is that the OFC is not necessary for STFP acquisition or systems consolidation, but it may serve a non-mnemonic function as the memory degrades over time / acase@tulane.edu

Thesis (Ph.D.)--University of California, San Francisco, 2010. / Source: Dissertation Abstracts International, Volume: 71-05, Section: B, page: . Adviser: Lily Y. Jan.

<p> The underlying goal of this dissertation is to understand how the amygdala, a brain region involved in establishing the emotional significance of sensory input, contributes to the processing of complex sounds. The general hypothesis is that communication calls of big brown bats (<i>Eptesicus fuscus</i>) transmit relevant information about social context that is reflected in the activity of amygdalar neurons. </p><p> The first specific aim analyzed social vocalizations emitted under a variety of behavioral contexts, and related vocalizations to an objective measure of internal physiological state by monitoring the heart rate of vocalizing bats. These experiments revealed a complex acoustic communication system among big brown bats in which acoustic cues and call structure signal the emotional state of a sender. </p><p> The second specific aim characterized the responsiveness of single neurons in the basolateral amygdala to a range of social syllables. Neurons typically respond to the majority of tested syllables, but effectively discriminate among vocalizations by varying the response duration. This novel coding strategy underscores the importance of persistent firing in the general functioning of the amygdala. </p><p> The third specific aim examined the influence of acoustic context by characterizing both the behavioral and neurophysiological responses to natural vocal sequences. Vocal sequences differentially modify the internal affective state of a listening bat, with lower aggression vocalizations evoking the greatest change in heart rate. Amygdalar neurons employ two different coding strategies: low background neurons respond selectively to very few stimuli, whereas high background neurons respond broadly to stimuli but demonstrate variation in response magnitude and timing. Neurons appear to discriminate the valence of stimuli, with aggression sequences evoking robust population-level responses across all sound levels. Further, vocal sequences show improved discrimination among stimuli compared to isolated syllables, and this improved discrimination is expressed in part by the timing of action potentials. </p><p> Taken together, these data support the hypothesis that big brown bat social vocalizations transmit relevant information about the social context that is encoded within the discharge pattern of amygdalar neurons ultimately responsible for coordinating appropriate social behaviors. I further propose that vocalization-evoked amygdalar activity will have significant impact on subsequent sensory processing and plasticity.</p>