Synthetic luteinizing hormone – releasing hormone (LH–RH) induces ovulation and stimulates release of secretory granules from the pituitary gonadotrophs of goldfish kept at 12 ± 1 °C, a temperature at which ovulation does not occur in control fish. Gonadal development is stimulated at doses too low to induce ovulation. Relatively high doses were required to induce ovulation; this may be related to the low experimental temperatures, although several other possibilities are discussed. Intracranial injections appeared to be only slightly more effective than intraperitoneal injections. A single type of gonadotroph containing two types of granules was identified at the ultrastructural level. Only the small, electron-dense granules are released after injection of synthetic LH–RH; the role of the large, less electron-dense granules is uncertain.

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