The effects of vasoactive intestinal polypeptide on the motility of human and guinea pig gallbladder

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Abstract
The effects of several preparations of vasoactive intestinal polypeptide (VIP) on the motility of strips of human and guinea pig gallbladder were investigated in vitro. VIP (10−12 to 10−6 M) had no measurable effects on the spontaneous activity, resting tone or cholecystokinin-octapeptide induced tone of human gallbladder strips. However, VIP (10−12 to 10−6 M) caused biphasic effects on the tone of guinea pig gallbladder strips. At low concentrations (10−12 to 10−10 M) contractions were observed that became smaller at higher concentrations (10−9 to 10−8 M). At still higher concentrations (10−7 to 10−6 M) relaxations were elicited. It appears that VIP is not as potent a relaxant of gallbladder muscle as first described. Human gallbladder tissue was totally unresponsive to the VIP preparations tested.