VPAC2 receptor activation mediates VIP enhancement of population spikes in the CA1 area of the hippocampus

The receptors mediating vasoactive intestinal polypeptide (VIP) enhancement of synaptic transmission to pyramidal cell bodies were investigated. RO 25-1553 (VPAC 2 agonist) mimicked the excitatory effect of VIP on population spike (PS) amplitude. [K 15 , R 16 , L 27 ] VIP (1-7)/GRF (8-27) (VPAC 1 agonist) caused only a small increase in PS amplitude. The effect of VPAC 2 agonist (but not of the VPAC 1 agonist) persisted upon blockade of GABAergic transmission and was strongly attenuated upon inhibition of PKA. In conclusion, VPAC 2 receptor activation mediates VIP enhancement of PS amplitude in the hippocampus essentially through a PKA-dependent mechanism.