Brain histamine mediates the bombesin-induced central activation of sympatho-adrenomedullary outflow.
Intracerebroventricular (i.c.v.) administration of bombesin (0.3 nmol) increased plasma levels of both adrenaline and noradrenaline in urethane anesthetized rats. These bombesin-induced increases were inhibited by i.c.v. pretreatment with pyrilamine, an H1-receptor antagonist. Ranitidine, an H2-receptor antagonist also inhibited the increase of adrenaline, however, its effective dose was much larger than that of pyrilamine. Furthermore, the bombesin-induced increase of noradrenaline was not effectively inhibited by ranitidine. In the next series, turnover of histamine was assessed by measuring accumulation of tele-methylhistamine (t-MH), a major metabolite of brain histamine. I.c.v. administration of bombesin (0.3-3 nmol) increased turnover of hypothalamic histamine, while its intravenous administration was without effect. The present results suggest that the bombesin-induced central activation of sympatho-adrenomedullary outflow is probably, at least in part, mediated through brain histaminergic neurons.
Okuma
Y
Y
Department of Pharmacology, Kochi Medical School, Japan.
Yokotani
K
K
Murakami
Y
Y
Osumi
Y
Y
D000313:Adrenal Medulla / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D001839:Bombesin / Q000008:administration & dosage / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism*; D004837:Epinephrine / Q000097:blood; D006632:Histamine / Q000502:physiology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010293:Pargyline / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D011899:Ranitidine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology
D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D006632:Histamine; D011899:Ranitidine; D010293:Pargyline; D011738:Pyrilamine; D001839:Bombesin; D009638:Norepinephrine; D004837:Epinephrine