A NOVEL SPECIFIC BINDING-SITE FOR HOMOPHTHALAZINES IN THE RAT-BRAIN

The specific binding sites of a homophthalazine, girisopam, in rat bra in have been localized by qualitative and quantitative autoradiography . This substance exerts strong anxiolytic and antipsychotic effects bo th in rodents and in humans. High labeling was present in all major co mponents of the extrapyramidal system, such as the caudate-putamen, gl obus pallidus, subthalamic nucleus, substantia nigra, and the extrapyr amidal portion of the accumbens nucleus and the olfactory tubercle, wh ile specific labeling was not seen in any other brain areas including the cerebral cortex, thalamus, cerebellum or brainstem areas. This nov el distribution of girisopam is consistent with its antipsychotic effe ct and anxiolytic properties and may provide a morphological basis for further studies to elucidate the mechanisms of action of homophthalaz ines in the central nervous system.