title: Effect of calcium on neurohumoral stimulation of feline colonic smooth muscle.
abstract: The purpose of this study was to compare the effect of altering the extracellular calcium ion concentration on bethanechol or octapeptide of cholecystokinin (OP-CCK) stimulation of the isolated transverse colon of the cat. Myoelectric activity was recorded with monopolar glass-pore electrodes. Bethanechol (10(-6) M) stimulated an increase in the number of slow waves with superimposed spike potentials to 85.5 +/- 5.3% (P less than 0.001) compared with the basal spike activity (8.9 +/- 1.4%). OP-CCK (4 x 10(-9)) also increased spike activity (80.7 +/- 3.8%, P less than 0.001), which was not inhibited by atropine, phentolamine, or propranolol. Addition of 0.0 mM calcium solution to the colonic smooth muscle abolished both slow-wave and spike activity, which returned after replacing 0.25 mM calcium in the solution. Bethanechol stimulated a greater increase in spike activity as the concentration of calcium was increased. OP-CCK stimulation of colonic spike activity was more sensitive to the extracellular calcium concentration than bethanechol stimulation. Verapamil had a minimal effect on bethanechol stimulation of colonic spike activity, but it inhibited the OP-CCK stimulation. These studies suggest that 1) OP-CCK appears to stimulate colonic smooth muscle directly and 2) OP-CCK requires the presence of a greater amount of extracellular ionic calcium in order to stimulate colonic spike activity compared with bethanechol.
mesh_terms: D000818:Animals; D001626:Bethanechol Compounds / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002415:Cats; D002766:Cholecystokinin / Q000494:pharmacology; D003106:Colon / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D008297:Male; D009130:Muscle, Smooth / Q000502:physiology*; D018377:Neurotransmitter Agents; D010446:Peptide Fragments / Q000494:pharmacology; D012844:Sincalide; D013268:Stimulation, Chemical
chemical_list: D001626:Bethanechol Compounds; D018377:Neurotransmitter Agents; D010446:Peptide Fragments; D002766:Cholecystokinin; D012844:Sincalide; D002118:Calcium