Effect of buspirone on thermal sensory and pain thresholds in human volunteers

BACKGROUND Buspirone is a partial 5-HT1A receptor agonist. Animal studies have shown that modulation of serotoninergic transmission at the 5-HT1A receptor can induce analgesia in acute pain models. However, no studies have been published so far on the effects of serotonin receptor agonists on pain perception in humans. METHODS The effects of buspirone (30 mg p.o.) on thermal sensory and pain thresholds were investigated in twelve female volunteers (26 +/- 2 yrs) in a prospective, randomized, double-blind, double-dummy, placebo-controlled study with morphine (10 mg i.v.) as positive control. RESULTS Morphine significantly increased the heat pain detection threshold (DeltaT: placebo 1.0 degrees C and 1.3 degrees C, p < 0.05) at 60 minutes. Buspirone caused mild sedation in six participants at 60 minutes, but was without effect on any of the measured parameters. CONCLUSION Buspirone in the maximal recommended dose was without significant effect on thermal pain. However, as it is only a partial agonist at the 5-HT1A receptor and also acts on other receptor types, the negative results of the present study do not rule out a possible analgesic effect of more specific 5-HT1A receptor agonists.