Neurochemistry and neurophysiology of buspirone and gepirone: interactions at presynaptic and postsynaptic 5-HT1A receptors.

Preclinical neurochemical studies indicate that buspirone and gepirone bind selectively to presynaptic (dorsal raphe) and postsynaptic (hippocampus, cortex) 5-hydroxytryptamine1A (5-HT1A) receptor binding sites. Furthermore, in functional neurochemical and electrophysiologic receptor studies, azapirones in general display partial agonist activity at postsynaptic 5-HT1A receptors linked negatively to adenyl cyclase and appear to demonstrate a similar profile on hippocampal CA1 pyramidal neurons sensitive to the effects of 5-HT. Through their action at presynaptic 5-HT1A receptors, these agents have been shown to dose-dependently inhibit cortical and hippocampal 5-HT synthesis while inhibiting the firing of 5-HT--containing dorsal raphe neurons, both in vitro and in vivo. These results suggest that the efficacy seen in clinical trials of anxiety and depression may be related to buspirone's and gepirone's complex interaction with presynaptic and postsynaptic 5-HT1A receptors, which initiate long-term changes in central 5-HT neurotransmission.