Effect of centrally administered neuropeptide Y on hypothalamic and hypophyseal proopiomelanocortin-derived peptides in the rat.
In a previous study, we have shown that neuropeptide Y inhibits the release of alpha-melanocyte-stimulating hormone from the rat hypothalamus in vitro. The aim of the present study was to investigate the possible effect of neuropeptide Y on the regulation of proopiomelanocortin-derived peptides in vivo. Rats received acute or chronic administration of neuropeptide Y in the lateral ventricle and the amount of alpha-melanocyte-stimulating hormone was measured in the hypothalamus and in the neurointermediate lobe of the pituitary. In the same experiments, the amounts of corticotropin-releasing factor and corticotropin were quantified in the hypothalamus and anterior pituitary, respectively. Acute treatment with synthetic neuropeptide Y (0.1 to 10 micrograms/rat) did not modify the amount of alpha-melanocyte-stimulating hormone in the hypothalamus. In contrast, chronic infusion of neuropeptide Y (1.25 micrograms/h) over a seven day period significantly decreased the hypothalamic content of alpha-melanocyte-stimulating hormone, suggesting that neuropeptide Y regulates the synthesis and/or the processing of proopiomelanocortin. Concurrently, we found that both acute and chronic infusion of neuropeptide Y induced a significant reduction in corticotropin-releasing factor in the hypothalamus as well as a significant decrease in alpha-melanocyte-stimulating hormone and corticotropin in the neurointermediate and anterior lobes, respectively. Quantitative in situ hybridization histochemistry showed that chronic administration of neuropeptide Y also caused a reduction of proopiomelanocortin messenger RNA levels both in the intermediate and anterior lobes of the pituitary. Administration of neuropeptide Y (10(-6) M) on perifused rat hypothalamic slices caused a significant increase in corticotropin-releasing factor release.(ABSTRACT TRUNCATED AT 250 WORDS)
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis; D015342:DNA Probes; D015870:Gene Expression / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D017403:In Situ Hybridization; D007276:Injections, Intraventricular; D008297:Male; D009478:Neuropeptide Y / Q000008:administration & dosage / Q000494:pharmacology*; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis* / Q000235:genetics; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D000521:alpha-MSH / Q000096:biosynthesis
D015342:DNA Probes; D009478:Neuropeptide Y; D000521:alpha-MSH; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone