We studied the effects of histamine (HA) antagonists on the facilitatory action of morphine (M) and β-endorphin (βE) on prolactin (PRL) release and the effect of α-fluoromethylhistidine (α-FMH, inhibitor of HA synthesis) on βE-induced PRL secretion. Male rats were injected intracerebroventricularly (i.c.v.) with mepyramine (MEP, H1-antagonist, 0.8 μmol/rat) or ranitidine (RAN, H2-antagonist, 0.4 μmol/rat) 10 min before M (6 mg/kg, intracarotid, i.a.) or βE (0.25 μg/rat, i.c.v.). α-FMH (200 μg/rat, i.c.v.) was administered 3 h before βE. 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 α-FMH modified βE-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 βE.
ASJC Scopus subject areas
- Pharmacology (medical)