Effects of cholecystokinin-octapeptide and cerulein on ovine digestive motility under cholinergic blockade

In sheep, contribution of cholinergic system to the control of gastrointestinal motility by cholecystokinin is unknown. Accordingly, in six non-fasted rams chronic experiments were conducted and the myoelectrical activity of abomasal antrum, duodenum and jejunum was recorded before and after injection of atropine (two doses), pirenzepine (two doses), hexamethonium or atropine plus hexamethonium followed or not by injection of three doses of cholecystokinin octapeptide or cerulein. In the course of the experiments performed, the anticholinergic drugs and hormones suppressed spike burst activity both in abomasal antrum and small bowel and inhibited the migrating myoelectric complex and ‘minute rhythm’. When the hormones were injected after cholinergic blockade, they induced longer inhibitory effects than cholinergic blockade alone. In the small bowel, some stimulatory effects were observed as well. The higher dose of pirenzepine and remaining anticholinergics induced rebound excitation in the small bowel, but when followed by cholecystokinin peptide administration, no rebound effect was denoted. Hexamethonium given alone or in combination with atropine followed by cholecystokinin peptide caused stronger inhibitory effect than that of atropine or pirenzepine. It is concluded that cooperation exists between the cholinergic system and cholecystokinin in the control of gastrointestinal motility in sheep and the role of nicotinic mechanisms is greater than that of muscarinic mechanisms. DOI: http://dx.doi.org/10.5281/zenodo.25401