VIP RECEPTORS ON CANINE SUBMUCOSAL SYNAPTOSOMES

The present study characterized [I-125]P binding to synaptosomes from the submucosa of canine small intestine. Studies of saturation, compet ition binding, and kinetic studies revealed high- and low-affinity bin ding sites. Studies with GTP-gamma-S and cholera toxin suggested that the receptor was coupled to a G-protein, possibly G(s). Competition wi th VIP analogs suggested that the N-terminal end of the molecule playe d the major role in determining affinity and that this receptor was fo r VIP, not PACAP. Cross-linking VIP to the receptor revealed a single peptide (M(r) congruent-to 60,000). We suggest that VIP may act to mod ulate mediator release from enteric nerve endings.