Stimulation of H3-histamine receptors increases the release of prolactin in male rats.
Histamine (HA) stimulates prolactin secretion via H1 and H2 receptors. In the present study, we examined the role of a third subtype of receptor recently described in brain, the H3-HA receptor, on prolactin secretion in male rats. R(-)alpha-methyl-HA (alpha-MHA), a selective H3 receptor agonist, was injected into the lateral ventricle of the brain in freely moving rats. alpha-MHA produced a dose-dependent (1-5 micrograms) and long-lasting increase in plasma prolactin levels. This increase was observed from 15 to 60 min after injection of alpha-MHA. Its stimulatory action was prevented by thioperamide (20 micrograms i.v.t), a selective H3 antagonist. This compound, injected intraventricularly, lacked effect by itself on basal plasma prolactin levels. Neither pyrilamine (H1 antagonist; 60 micrograms i.v.t.) nor ranitidine (H2 antagonist; 60 micrograms i.v.t.) affected alpha-MHA-induced prolactin release. The stimulatory effect was still present when brain HA was depleted by alpha-fluoromethylhistidine (30 mg/kg i.p.). Our findings suggest that alpha-MHA evokes prolactin release by activation of postsynaptic H3 receptors.
Navarro
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Laboratorio de Investigaciones Cerebrales (LINCE-CONICET), Facultad de Ciencias Medicas, Universidad Nacional de Cuyo, Mendoza, Argentina.
Otoya
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Donoso
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D000818:Animals; D001921:Brain / Q000187:drug effects; D007276:Injections, Intraventricular; D007700:Kinetics; D008297:Male; D008761:Methylhistamines / Q000008:administration & dosage / Q000494:pharmacology; D008762:Methylhistidines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011968:Receptors, Histamine / Q000502:physiology*
D008761:Methylhistamines; D008762:Methylhistidines; D010880:Piperidines; D011968:Receptors, Histamine; C069357:alpha-methylhistamine; C028309:alpha-fluoromethylhistidine; D011388:Prolactin; C052075:thioperamide