Autoradiographic evidence for the heterogeneity of 5-HT1 sites in the rat brain

The distribution of the binding sites of a new, potent agonist of serotonin (5-HT), 8-OH-N,N-dipropoyl-2-aminotetralin (PAT), was studied in the rat brain with the quantitative autoradiographic technique utilizing tritium-sensitive LKB film. The localization of ³H]PAT binding sites was very similar to that of ³H]5-HT binding sites, except in some discrete regions (choroid plexus, striatum, area preoptica lateralis, subiculum, and substantia nigra), which exhibited very low levels of labeling with ³H]PAT and high levels with ³H]5-HT. These results indicate that 5-HT₁ receptors are heterogeneous, and that ³H]PAT recognizes only a 5-HT₅ subclass (called 5-HT_1A).