Effects of porcine gastrin releasing peptide (GRP) on canine antral motility and gastrin release in vivo.

The effect of GRP on the in vivo canine antrum was investigated. GRP caused a dose-dependent increase in antral gastrin output which was not significantly altered by administration of tetrodotoxin. The higher doses of GRP administered also caused excitation of antral motility which was abolished by tetrodotoxin, a finding in contrast to previous in vitro results demonstrating bombesin-induced antral smooth muscle contraction to be tetrodotoxin-resistant. These data suggest that in the in vivo canine model GRP causes antral gastrin release via non-neurally mediated mechanisms (probably by acting directly on the G-cell) and excites antral motility via neurally-mediated mechanisms.