<prompt> The following 5-HT receptor is not a G-protein coupled receptor5-HT15-HT25-HT35-HT4  <response>: Mech of action:- All 5-HT receptors except 5-HT3 are G protein coupled receptors which function through decreasing 5-HT1 or increasing 5-HT4, 5-HT6, 5-HT7 cAMP production or by generating IP3 DAG 5-HT2 as second messengers. The 5-HT3 is a ligand gated cation Na,K channel which on activation elicits fast depolarization. Ref:- kd tripathi; pg num:-171 