PT - JOURNAL ARTICLE AU - R F Coburn AU - T Yamaguchi TI - Membrane potential-dependent and-independent tension in the canine tracheal muscle. DP - 1977 May 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 276--284 VI - 201 IP - 2 4099 - http://jpet.aspetjournals.org/content/201/2/276.short 4100 - http://jpet.aspetjournals.org/content/201/2/276.full SO - J Pharmacol Exp Ther1977 May 01; 201 AB - We used the double sucrose gap apparatus to describe properties of electromechanical coupling in canine trachealis muscle, during infusion of elevated K+ and 5-hydroxytryptamine (5-HT). With 59 mM K+ and 5-HT, quasi-steady-state relationships of membrane depolarization and tension indicate electromechanical coupling, but for a given increase in tension much smaller membrane depolarizations were seen with 5-HT than with 59 mM K+. Evoked displacements of the membrane potential with anodal or cathodal current caused relaxations or contractions, respectively, and graded displacements resulted in graded tension changes. Reversal of 59 mM K+ membrane depolarization with long anodal current pulses resulted in nearly complete reversal of K+ tension, but reversal of 5-HT membrane depolarization caused tension reversal of only 20 to 40%. Data partially define electromechanical coupling in canine trachealis muscle provide evidence for membrane potential-independent tension with 5-HT at concentrations giving near threshold to maximal 5-HT tension.