The Coupling of Electrical and Mechanical Activities in Intestinal Smooth Muscle in Relation to Metabolism*

Abstract

S a n d o z P h a r m a c e u t i c a l s , R e s e a r c h Department, Pharmacology S e c t i o n , Hanover, N. J .T h e t a e n i a coli is a narrow band of smooth muscle running longitudinally on t h e ventral and dorsal s u r f a c e s of the caecum in certain s p e c i e s . T h e purpose of t h i s presentation is t o review t h e e x i s t i n g information on t h e physiology and biochemistry of t h e taenia coli of t h e guinea pig. T h e information available r e s u l t s largely from t h e work of E. Biilbring in collaboration with E. Bueding, J.Axelsson and P. J. Goodford. U n l e s s otherwise stipulated, t h e material in t h i s paper refers exclusively to the t a e n i a c o l i of the guinea Pig.In 1954, Bulbring reported on a s e r i e s of experiments in which simultaneous measurements of membrane potential, action potent i a l s and isometric t e n s i o n of taenia coli were made. It w a s found that the membrane potential averaged about 60 mV when the muscle w a s a t i t s i n situ length and fell t o 43 m V when the muscle w a s stretched. T h e s e v a l u e s were found t o b e the mean v a l u e s of t h e membrane potential which w a s fluctuating in a manner related to the spontaneous rhythm. P e r i o d s of higher tension w e r e found to b e a s s o c i a t e d with lower membrane potentials and increased r a t e s of s p i k e discharge, while periods of lower tension were a s s o c i a t e d with higher membrane potentials and reduced s p i k e frequency. T h e s e measurements were made using intracellular recording techniques.In 1958, Burnstock and Straub4 described an adaption of t h e s u c r o s e gap method of StPmpfil,' using external electrodes, t o t h e study of membrane and action potentials of smooth muscle s t r i p s from t h e taenia coli. V a l u e s for the resting membrane potential obtained by t h i s method were comparable t o t h o s e previously obtained with microelectrodes, and the method offered the advantage that quick changes of t h e bathing solution were p o s s i b l e so that continuous recordings could b e made of the e n t i r e s e q u e n c e of c h a n g e s c a u s e d by t e s t solutions. T h e chamber containing the muscle w a s further modified by Bulbring, Burnstock and Holman6 so t h a t t h e muscle could b e stimulated electrically and nieasurements of isometric tension could b e made simultaneously.' *Thin paper, illustrated with slide8. wan Presented at a meeting of t h e Seetion on May 11, 1964. 902

Effects of Factors Inhibiting Tension Development on Oxygen Consumption of Guinea Pig Taenia Coli in High K Medium

“…The activity of the membrane persisted for several hours in the absence of glucose but the tension response declined more rapidly, generally disappearing in 1---2 hours. Timms (6) described that after only two or three minutes exposure to a glucose-free medium, the glucose available within the taenia coli was reduced to a very low level (about 2-5% of normal level) and this level declined further but at a very slow rate (only further 10 percent in next 30 minutes). And it was extremely difficult to deplete glycogen from taenia coli merely by removing external glucose.…”