The role of central histaminergic neurons in head-twitches induced by p-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 administration of histamine (HA), which at doses could not induce this response, potentiated about 2-3 fold of the total number of p-OHA-induced this response. Pretreatment with a histidine decarboxylase inhibitor, α-fluoromethylhistidine, 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 antagonist. These results clearly indicate that central HA neuronal systems may, 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.