Localizations of neuropeptides in the brain and regulation of pituitary hormone secretion.

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1. Effects of cholecystokinin(CCK) and substance P(SP) on pituitary hormone Release. A cammula containing a mixture of CCK cholesterol(1:1 or 5:3 by weight) and one containing a mexture of SP and cholesterol(1:1) were implanted into the mediam eminence of male rats. CCK reduced serum luteinizing hormone(LH) but not follicle stimulating hormone, prolactin and thyroid stimulating hormone(TSH) concentrations; SP reduced only serum TSH concentrations. CCK implanted into the ventromedial or arcuate nuclues failed to have any effect on serum LH concentration. It is thus concluded that CCK inhibits the release of LH, and SP inhibits the release of TSH, probably by inhibiting LH-releasing hormone and TSH-releaseing hormone sectetion from their respective axon terminals in the median eminence.2. An immunohistochemical study of neuropeptides in the central nervous system of amphioxus. Neurons with perikarys and/or fibers showing immunoreactions to antisera against Met-enkephalin, b-endorphin, arginine vasopressin, oxytocin, angiotensin II and carp urotensin I were detected. Met-enkiphalin immunoreactive material was found to accumulate densely in the localized spors. small tissue spaces were often seen adjacent to the accumulated material, suggesting possible release and an endoctine nature of this substance. It was surmized that the arginine vasopressin-immunoreactive fibers had axo-axonic and axo-somatic contacts with the Rohde cell. No immunoreactions to antisera against atrial netriuretic polypeptide, corticotropin-releasing hormone and Leu-enkephalin were detected in the central nervous system.3. Atrial natriuretic polypeptide (ANp) in the fish brain. The immunohistochemical localization of ANP was studied by the PAP method using hANP antiserum. immunopositive neurons were found in the ependymal layer of the optic tectum in the rainbow trout. They extended axons toward the surface of the optic tectum.