Is histamine an anticonvulsive inhibitory transmitter?

This study was done to investigate the possible role of histaminergic systems in electroshock seizures. Brain histamine concentrations in rats were elevated by metoprine (i.p.), an inhibitor of histamine-N-methyltransferase. Animals were tested for their response to maximal electroshock (MES) at different times after the injection. Metoprine raised brain histamine concentrations and inhibited maximal hindleg extension after MES in a dose-dependent manner. Sensitivity to seizures correlated inversely with histamine concentrations. These results suggest that histaminergic neurones are involved in mechanisms which inhibit generalizations of epileptic discharges in the brain.