The effect of antihistamine drugs on the neuroleptic-induced catalepsy.

The effect of atropine on the spiperone- or reserpine-induced catalepsy was compared with the effect pure antihistamines (chlorcyclizine, diphenhydramine, mepyramine) and antiserotonin -- antihistamine drugs (cyproheptadine, danitracen). All the drugs were used in equipotent doses in respect of their central cholinolytic action, assassed previously on the basis of the tremorine test. The potency of the antiserotonin action of chlorcyclizine, diphenhydramine and mepyramine was estimated by assessing the ID50 values of these compounds in the test based on antagonism to L-5-hydroxytryptophan action in the mouse. The spiperone-induced catelepsy, was most effectively inhibited by classical histaminolytics and less by drugs of a combined antiserotonin and antihistamine action. For the reserpine-induced catalepsy, differences in action of the two groups of drugs were less distinct. In both cases atropine produced the weakest anticataleptic effect. Amodiaquine, an inhibitor of histamine degradation, enhanced the catalepsy induced by either neuroleptic (the reserpine-induced catalepsy in a statistically significant menner). A possibility that the anticataleptic action of chlorcyclizine, cyproheptadine, diphenhydramine, mepyrymine and danitracen depends on the blockade of the histamine receptors in the brain is discussed.