Shu-ichi Kojima
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)