<prompt> Mechanism of action of buspirone is?5 HT1A paial agonism.5 HT1B antagonism.5 HT1B paial agonism.5 HT2C antagonism.  <response>: Ans. A. HT1A paial agonism5 HT1A:Presynaptic autoreceptor.Modulates serotonin release.Paial 5 HT1A agonists:Buspirone, isapirone, gepirone.Useful as anti-anxiety drug. 