A selective role for brain histamine in prolactin release induced by opiates.
We studied the effects of histamine (HA) antagonists on the facilitatory action of morphine (M) and beta-endorphin (beta E) on prolactin (PRL) release and the effect of alpha-fluoromethylhistidine (alpha-FMH, inhibitor of HA synthesis) on beta E-induced PRL secretion. Male rats were injected intracerebroventricularly (i.c.v.) with mepyramine (MEP, H1-antagonist, 0.8 mumol/rat) or ranitidine (RAN, H2-antagonist, 0.4 mumol/rat) 10 min before M (6 mg/kg, intracarotid, i.a.) or beta E (0.25 micrograms/rat, i.c.v.). alpha-FMH (200 micrograms/rat, i.c.v.) was administered 3 h before beta E. Plasma PRL levels were measured at various times before and after drug treatment. RAN but not MEP significantly reduced PRL release induced by M whereas neither HA-antagonists nor alpha-FMH modified beta E-induced PRL release. The results obtained show that brain HA contributes through activation of H2-receptors to the PRL facilitatory action of M but not of beta E.
Netti
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C
Department of Pharmacology, Chemotherapy and Medical Toxicology, University of Milan, Italy.
Guidobono
F
F
Sibilia
V
V
Pagani
F
F
Villa
I
I
Pecile
A
A
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D006632:Histamine / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D008762:Methylhistidines / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D011738:Pyrilamine / Q000494:pharmacology; D011899:Ranitidine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin / Q000494:pharmacology*
D008762:Methylhistidines; D001615:beta-Endorphin; C028309:alpha-fluoromethylhistidine; D006632:Histamine; D011899:Ranitidine; D011388:Prolactin; D011738:Pyrilamine