Substance P induced hydrolysis of inositol phospholipids in guinea-pig ileum and rat hypothalamus.

The recent development of a sensitive assay procedure for monitoring the hydrolysis of inositol phospholipids allowed the detection of substance P-induced lipid hydrolysis in tissue slices of rat hypothalamus and guinea-pig ileum longitudinal smooth muscle. The EC50 values observed for substance P were similar on both tissues and corresponded well with the value previously reported for the rat parotid. Furthermore, the structure-activity profile for this response on all three tissues was similar and closely resembled that for ileum contraction. We therefore suggest that these three functionally distinct tissues possess the same subtype of substance P receptor coupled to inositol phospholipid hydrolysis, and that this receptor has the characteristics of the previously reported SP-P subtype.