N,N-di-n-propylserotonin: binding at serotonin binding sites and a comparison with 8-hydroxy-2-(di-n-propylamino)tetralin

8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) is a serotonergic agonist with high affinity and selectivity for a particular population of central serotonin (5-HT) binding sites (i.e., 5-HT1A sites). Because the selectivity of 8-OH-DPAT may be due to the terminal amine substituents, the di-n-propyl analogue of 5-HT (i.e., 4) and of 5-methoxytryptamine (i.e., 5) were prepared and compared with 8-OH-DPAT with respect to their binding profile. Unlike 8-OH-DPAT, neither compound 4 nor 5 displays selectivity for 5-HT1A vs 5-HT2 sites. Consistent with these results, stimulus generalization occurs with 5 both in rats trained to discriminate 8-OH-DPAT from saline and in rats trained to discriminate the 5-HT2 agonist DOM from saline. The results of this study suggest that it is not the N,N-dipropyl groups that account for selectivity, but, rather, it is some feature associated with the pyrrole portion of the indolylalkanamines that is important.