Effects of lipopolysaccharide on neurokinin A content and release in the hypothalamic-pituitary axis.
The administration of bacterial lipopolysaccharide (LPS) markedly affects pituitary secretion, and its effects are probably mediated by cytokines produced by immune cells or by the hypothalamo-pituitary axis itself. Since neurokinin A (NKA) plays a role in inflammatory responses and is involved in the control of prolactin secretion, we examined the in vivo effect of LPS on the concentration of NKA in hypothalamus and pituitary (assessed by RIA) and serum prolactin levels in male rats. One hour after the intraperitoneal administration of LPS (250 microg/rat), NKA content was decreased in the posterior pituitary but not in the hypothalamus or anterior pituitary. Three hours after injection, LPS decreased NKA concentration in the hypothalamus and anterior and posterior pituitary. In all the conditions tested, LPS significantly decreased serum prolactin. We also examined the in vitro effects of LPS (10 microg/ml), interleukin-6 (IL-6, 10 ng/ml) and tumor necrosis factor alpha (TNF-alpha, 50 ng/ml) on hypothalamic NKA release. Interleukin-6 increased NKA release without modifying hypothalamic NKA concentration, whereas neither LPS nor TNF-alpha affected them. Our results suggest that IL-6 may be involved in the increase of hypothalamic NKA release induced by LPS. NKA could participate in neuroendocrine responses to endotoxin challenge.
De Laurentiis
Andrea
A
Centro de Investigaciones en Reproducción, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, piso 10, Buenos Aires 1121, Argentina.
Candolfi
Marianela
M
Pisera
Daniel
D
Seilicovich
Adriana
A
D000818:Animals; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007274:Injections, Intraperitoneal; D015850:Interleukin-6 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D015288:Neurokinin A / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D015850:Interleukin-6; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D015288:Neurokinin A; D011388:Prolactin