Department of Pharmacology, Dokkyo University School of Medicine, Mibu, Tochigi 321-02, Japan
Abstract: In the guinea pig distal colon, calcitonin gene-related peptide (CGRP, 0.1 - 30 nM) produced a concentration-dependent inhibition in electrically-evoked nonadrenergic noncholinergic (NANC) contractions and exogenous substance P-induced contractions. Both the inhibitory actions of CGRP were insensitive to human CGRP (8 - 37) (1 - 3 microM), a CGRP1 receptor antagonist. These results indicate that in the distal colon, CGRP inhibits electrically-evoked NANC contraction through a postjunctional mechanism, in contrast to our previously described results that CGRP enhances the NANC contraction of guinea pig proximal colon via a prejunctinal mechanism.
Keywords: Calcitonin gene-related peptide (CGRP), Nonadrenergic noncholinergic (NANC) transmission, Colon (guinea pig)