Changes in Histamine Metabolism in the Mouse Hypothalamus Induced by Acute Administration of Ethanol

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Abstract
The effect of acute ethanol administration on histamine (HA) dynamics was examined in the mouse hypothalamus. The steady‐state level of HA did not change after intraperitoneal administration of ethanol (0.5–5 g/kg), whereas the level of tele‐methylhistamine (t‐MH), a predominant metabolite of brain HA, increased when 3 and 5 g/kg of ethanol was given. Pargyline hydrochloride (80 mg/kg, i.p.) increased the level of t‐MH by 72.2% 90 min after the treatment. Ethanol at any dose given did not significantly affect the t‐MH level in the pargyline‐pretreated mice. Decrease in the t‐MH level induced by metoprine (10 mg/kg, i.p.), an inhibitor of HA‐N‐methyltransferase, was suppressed by ethanol (5 g/kg), thereby suggesting inhibition of the elimination of brain t‐MH. Ethanol (5 g/kg) significantly delayed the depletion of HA induced by (S)‐α‐fluoromethylhistidine (50 mg/kg, i.v.), a specific inhibitor of histidine decarboxylase. Therefore, a large dose of ethanol apparently decreases HA turnover in the mouse hypothalamus.