DISTRIBUTION AND CHARACTERIZATION OF THE [H-3] GRANISETRON-LABELED 5-HT3 RECEPTOR IN THE HUMAN FOREBRAIN

The present study has demonstrated the distribution of [H-3]granisetro n-labelled 5-HT3, receptors in the human forebrain with relatively hig h levels of this receptor in homogenates of hippocampus, caudate nucle us, putamen, nucleus accumbens and amygdala. Lower levels of 5-HT, rec eptors were found in other brain regions and the cervical vagus nerve. Pharmacological characterization of the labelled 5-HT3, receptor in h uman putamen homogenates identified a relatively low affinity for d-tu bocurarine compared to the 5-HT, receptor in NG108-15 neuroblastoma-gl ioma cell homogenates. In contrast, the affinities of 19 other 5-HT, r eceptor ligands were not significantly different for the [H-3]graniset ron-labelled receptor in these two preparations. Such findings indicat e that the human putamen 5-HT3 recep a unique pharmacology which may h ave significance given the reported clinical potential of compounds ac tive at this receptor when assessed in animal models of disease.