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Both glutamate and gamma-aminobutyric acid (GABA) are involved in pituitary hormone release in fish. Glutamate serves 2 purposes, both as a neurotransmitter and as a precursor for GABA synthesis. Glutamate can be catabolized to GABA by the actions of 2 distinct but related enzymes, glutamate decarboxylase 65 (GAD65) and GAD67. They derive from 2 different(More)
Models are essential for the full understanding of neuroendocrine control processes. In this regard fish offer a rich source of biological material. They have diverse growth and reproductive strategies, inhabiting most of the Earth's aquatic ecological niches. Fish possess many of the common vertebrate features but also offer several unique aspects to allow(More)
Double-labelling studies at the electron microscopic level demonstrated that gamma-aminobutyric acid (GABA)-immunoreactive nerve endings are associated with growth-hormone-secreting cells in the proximal pars distalis of the goldfish pituitary gland, suggesting that GABA may be important for the control of growth hormone release in this species. An in vitro(More)
The goldfish sex pheromone system is the best understood among the teleost fishes. Pheromones in this species are unspecialized hormonal products, which are released in ratios that vary with reproductive status. This study examined behavioral responses of male goldfish to three steroidal components of the female preovulatory pheromone:(More)
This study investigated the effect of water temperature on the synthesis of the amino acid neurotransmitter gamma-aminobutyric acid (GABA). In goldfish, GABA stimulates the release of pituitary gonadotropin-II (GTH-II), which regulates gonadal function. Fish were maintained in water of 11, 18, or 24 degrees. In the female and male goldfish, GABA synthesis(More)
Testosterone and oestradiol can modulate GABA synthesis in sexually regressed goldfish. Here we investigated their effects on the mRNA expression of two isoforms of the GABA synthesizing enzyme glutamate decarboxylase (GAD(65) and GAD(67), EC Full-length GAD clones were isolated from a goldfish cDNA library and sequenced. Goldfish GAD(65) encodes(More)
Previous studies in goldfish (Carassius auratus) demonstrate that milt (sperm and seminal fluid) volume is increased both by a preovulatory steroidal pheromone, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P), that acts by increasing serum concentrations of gonadotropin II (GTH-II), and by a post-ovulatory prostaglandin (PG) pheromone, that acts(More)
Milt volume in goldfish is increased by female steroid and prostaglandin pheromones, by exposure to males with elevated gonadotropin levels, and by isolation from conspecifies. This study examined various aspects of the isolation effect on milt volume and serum gonadotropin II (GTH II). The latency of isolation-induced milt increase in this study (12-24 hr)(More)