Electrophysiological study of the action of neurotensin on the smooth muscle of the guinea-pig taenia coli.
The effects of neurotensin on the membrane potential and conductance, and on the tension of the guinea-pig taenia coli were investigated using the sucrose gap method. In preparations spontaneously active at 37 degrees C, neurotensin (0.5--10 nM) increased the frequency of spikes and induced a smooth muscle membrane depolarization which led to a block of spike discharges. These electrical events were accompanied by phasic and tonic contractions of the smooth muscle. At 20 degrees C the guinea-pig taenia coli exhibited little or no spontaneous activity. Neurotensin (50 nM) rapidly depolarized the smooth muscle membrane and increased its conductance. Concentration--response curves of neurotensin-induced depolarization and contraction gave an EC50 of 1.7 nM and 4.5 nM respectively, with a maximally effective concentration of peptide around 50 nM for both effects. Studies in modified or substituted salt solutions indicated that the neurotensin-induced increase in smooth muscle membrane conductance was primarily due to an increase in Na+ and Ca2+ conductances.
D000818:Animals; D002118:Calcium; D003106:Colon / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D007473:Ion Channels; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009496:Neurotensin / Q000494:pharmacology*; D012964:Sodium
D007473:Ion Channels; D009496:Neurotensin; D012964:Sodium; D002118:Calcium