SEVERAL HYPOTHALAMIC PEPTIDES STIMULATE THYROTROPIN AND GROWTH-HORMONE SECRETION BY ADULT TURTLE PITUITARY-GLANDS

1. Pituitary glands from adults of two species of emydid turtles, Chrysemys picta bellii and Trachemys (Pseudemys) scripta elegans, were superfused with several neuropeptides to study thyrotropin (TSH) and growth hormone (GH) secretory regulation. 2. Secretion of both TSH and GH by hemipituitaries from female C. picta belli were stimulated by increasing doses (from 0.1 to 1000 nM) of thyrotropin-releasing hormone (TRH), ovine corticotropin-releasing hormone (CRH) or rat growth hormone-releasing hormone (GHRH). 3. Similar results were obtained using whole pituitary glands from male and female T. scripta elegans. 4. These findings show that several neuropeptides, which can stimulate TSH and GH secretion by hatching turtle pituitaries, are also active in adults. Thus, this plasticity in responsiveness to neuropeptides is not restricted to the undifferentiated, immature animal.