AUTORADIOGRAPHIC LOCALIZATION AND QUANTITATIVE-DETERMINATION OF SPECIFIC BINDING-SITES OF ANXIOLYTIC HOMOPHTHALAZINES (FORMERLY CALLED 2,3-BENZODIAZEPINES) IN THE STRIATO-PALLIDO-NIGRAL SYSTEM OF RATS

Homophthalazines (2,3-benzodiazepin-derivatives, such as tofisopam, ne risopam, girisopam) constitute a drug family with strong anxiolytic an d antipsychotic potencies. By autoradiography, all of these drugs show ed a specific distribution pattern of binding sites exclusively in bra in areas which relate to the striato-pallido-nigral system, while no s pecific label was found in any other brain areas in the rat. Quantitat ive analyses of the autoradiograms by computerized densitometry, as we ll as by a receptor binding assay on 32 microdissected brain areas sho wed very high concentrations of tritiated homophthalazines in the glob us pallidus, caudate nucleus, putamen and the substantia nigra. Relati vely high density of binding sites was measured in the nucleus accumbe ns, the olfactory tubercle, the entopeduncular nucleus and the subthal amic nucleus. Concentrations measured in the cerebral cortical areas, cerebellum or brainstem nuclei did not differ from the background. No significant differences were found between the homophthalazines invest igated in terms of the distribution patterns or density of binding sit es.