Neuroendocrine regulation and transduction mechanisms in pituitary hormone release in fish

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Pituitary luteinizing hormone (LH) and growth hormone (GH) are important regulators of reproduction and growth in vertebrates. Multiple stimulatory and inhibitory brain hypothalamic neurohormones in turn control LH and GH secretion and production. Thus, studying the mechanisms by which the effects of these neurohormones are manifested at the level of the pituitary cells is important for understanding the physiological control of growth and reproduction. In goldfish, LH- and GH-cells share common, as well as distinct, regulators. For example, two gonadotropin-releasing hormones (GnRH2 and GnRH3), pituitary adenylate cyclase-activating polypeptide (PACAP) and ghrelin (gGRLN) stimulate both LH and GH secretion while dopamine (DA) inhibits LH, but stimulates GH, release. In contrast, GH-releasing hormone (gGHRH) stimulates GH, but attenuates LH, secretion. Understanding how the intracellular cellular changes (signal tranduction events) effected by these neurohormones interact to mediate their influences on LH and GH release and synthesis is integral to studying the physiological control of reproduction and growth. We have previously focused on how extracellular and intracellular Ca