THE ROLE OF CENTRAL HISTAMINERGIC NEURONS IN HEAD-TWITCHES INDUCED BYP-HYDROXYAMPHETAMINE

The effect of some histamine H-1- and H-2-receptor antagonists on the mouse head-twitches induced by intracerebroventricular injection of p- hydroxyamphetamine (p-OHA) has been studied. Simultaneous administrati on of histamine (HA), which at doses could not induce this response, p otentiated about 2-3 fold of the total number of p-OHA-induced this re sponse. Pretreatment with a histidine decarboxylase inhibitor, alpha-f luoromethylhistidine, significantly reduced this response induced by p -OHA. This blockade was also found after pretreatment with either H-1- receptor antagonist, diphenhydramine, chlorpheniramine or promethazine , but blockade was not found after cimetidine, an H-2-receptor antagon ist. These results clearly indicate that central HA neuronal systems m ay, at least in part, participate in to p-OHA-induced head-twitches in mice, by way of the brain serotonergic neuronal system, which system is mainly responsible for inducing this animal response.