Expression of cholecystokinin A receptors in neurons innervating the rat stomach and intestine

Background & Aims: Two distinct receptors, cholecystokinin (CCK)-A and CCK- B, mediate CCK effects in the digestive system. The aim of this study was t o elucidate the cellular sites of expression of CCK-A receptor in the rat s tomach and small intestine. Methods: We developed and characterized an anti body to the N-terminal region (LDQPQPSKEWQSA) of rat CCK-A receptor and use d it for localization studies with immunohistochemistry. Results: Specifici ty of the antiserum was demonstrated by (1) detection of a broad band at 85 -95 kilodaltons in Western blots of membranes from CCK-A receptor CHO-trans fected cells; (2) cell surface staining of CCK-A receptor-transfected cells , (3) translocation of CCK-A receptor immunostaining in CCK-A receptor-tran sfected cells after exposure to CCK; and (4) abolition of tissue immunostai ning by preadsorbtion of the antibody with the peptide used for immunizatio n. CCK-A receptor immunoreactivity was localized to myenteric neurons and t o fibers in the muscle and mucosa. In the stomach, myenteric neurons and mu cosal fibers were abundant. Many CCK-A receptor myenteric neurons contained the inhibitory transmitter vasoactive intestinal polypeptide, and some wer e immunoreactive for the excitatory transmitter substance P. Subdiaphragmat ic vagotomy reduced the density of CCK-A receptor fibers in the gastric muc osa by approximately 50%, whereas celiac/superior mesenteric ganglionectomy had no detectable effect on fiber density. Conclusions: CCK-A receptor is expressed in functionally distinct neurons of the gastrointestinal tract. C CK-A receptor may mediate reflexes stimulated by CCK through the release of other transmitters from neurons bearing the receptor.