Effects of substance P on pancreatic exocrine secretion stimulated by secretin, dopamine and cholecystokinin in dogs.

The effect of substance P (SP) on pancreatic exocrine responses to exogenous cholecystokinin, secretin, and dopamine, were studied in the isolated and blood-perfused pancreas of dogs. Intra-arterial injection of SP had a significant biphasic effect on pancreatic secretion: an initial transient inhibition, followed by an increase in the secretion stimulated by the infusion of cholecystokinin. However, SP caused only an inhibition of secretion stimulated by the infusion of secretin and dopamine. SP increased protein concentration but not bicarbonate concentration in juice stimulated by cholecystokinin, but SP did not affect significantly either protein or bicarbonate concentrations in juice stimulated by secretin and dopamine. These results suggest that SP has greater effects on the pancreatic secretion stimulated by cholecystokinin than that stimulated by secretin and dopamine.