DIFFERENT SUBSTANCE-P RECEPTORS ARE FOUND ON MUCOSAL EPITHELIAL-CELLS AND SUBMUCOUS NEURONS OF THE GUINEA-PIG SMALL-INTESTINE

Abstract

The action of substance P (SP) on mucosal ion transport has been investigated in the guinea-pig small intestine. Segments of intestine were dissected free of external muscle and myenteric plexus and mounted in Ussing chambers. Short-circuit current (Isc) was measured as an indication of net ion transport across the tissue. SP (greater than 10(-10) M) added to the submucosal side of the tissue caused a transient increase in Isc. Tetrodotoxin (TTX, 10(-7) M) decreased the maximum SP response to 11% of the control value. TTX completely inhibited the response to electrical field stimulation but had no effect on Isc increases due to carbachol or theophylline. In the presence of hyoscine (10(-7) M..