Neuroleptic drugs and 5HT1 receptor: different potencies of various neuroleptic drugs on 5HT1 receptors in discrete regions of the rat brain.

The potencies of various neuroleptic drugs (zotepine, chlorpromazine-HCl, haloperidol and spiperone) on serotonin1 (5HT1) receptors were examined in discrete rat brain regions using the radio receptor assay. The potencies of the neuroleptic drugs on 5HT1 receptors were clearly differentiated in the discrete brain regions: zotepine was the most potent in the frontal cortex, striatum and brain stem; spiperone was the most potent in the hippocampus. Furthermore, zotepine and chlorpromazine-HCl produced no great differences among the various regional 5HT1 receptors, while butyrophenones, haloperidol and spiperone showed remarkable differences. These findings demonstrate that the neuroleptic drugs can be differentiated according to their different affinities for regionally discrete 5HT1 receptors in the brain. This suggests that 5HT1 receptors may be able to be classified into two subtypes: the zotepine and chlorpromazine-HCl group having a high affinity for one subtype and butyrophenones a high affinity for the other.