Central and peripheral motor effects of galanin on the duodenojejunum and colon in fed rats

The effects of intraperitoneal, intrathecal and intracerebroventricular injections of the peptide galanin (GAL) on duodenojejunal and colonic motility were studied in conscious fed rats. At 0.3-3.0 nmol/rat, intraperitoneal GAL restored the 'fasted pattern' of duodenojejunal activity, i.e. the migrating myo-electric complex (MMC) was restored for a short period of time, and the MMC frequency was not significantly different from that observed before feeding. In addition, the activity of the proximal but not of the distal colon was significantly increased by GAL administration. The intracerebroventricular administration of GAL (0.03-0.3 nmol/rat) induced an MMC fasted pattern on the duodenojejunum after a latency period of about 1 h. In these experiments proximal colonic motor activity was significantly increased for 120-180 min. GAL given intrathecally (0.03-0.3 nmol/rat) induced a long-lasting fasted pattern of the intestinal activity within 10-20 min which was not dose dependent in duration, while the motility index of the proximal colon was significantly increased. Pretreatment with naloxone prevented the specific effects of GAL, given intracerebroventricularly or intrathecally, on the duodenojejunum and colon and the colonic response, but not the restoration of the MMC pattern on the duodenojejunum, induced by GAL given intraperitoneally. Ketoprofen pretreatment was completely ineffective. These observations indicate a plurality of sites of action of GAL on digestive tract motility including local duodenal receptors and suggest the importance of a spinal component in the control of motility by GAL when given intrathecally. Moreover the present results indicate the involvement of opioid receptors in the fasted pattern induced by GAL given intracerebroventricularly or intrathecally and in the colonic effects regardless of the route of administration.