Phenol increases twitch tension by increasing Ca2+ transients in intact single Xenopus myofibers

Abstract

Phenol is a neurolytic agent used for management of spasticity in patients with neuron injury. The effects of phenol on skeletal muscle function are unknown. We investigated the effects of phenol on force production and Ca2+ release in intact single Xenopus skeletal muscle fibers. To determine the relationship between force production and Ca2+ release in the absence and presence of phenol (0.005% – 0.05% w/v), intact single muscle fibers were dissected and microinjected with FURA‐2 followed by electrically stimulated single‐twitches and tetanic contractions (1–150Hz, 250 ms train, 2 ms stimulus, 8–10V). During single‐twitches at activation frequencies that elicited far less force than maximal, phenol reversibly increased the force and peak Ca2+ ratios compared to the untreated condition in a concentration‐dependent manner (from 10 ± 4% to 57 ± 10% of maximum tetanic force and from 47 ± 11% to 68 ± 10% of the maximum FURA‐2 ratio, both at 0.05% phenol, P<0.01). At higher concentrations (>0.05%), phenol completely blocked force production. These results suggest that phenol increases twitch force by increasing Ca2+ release from the sarcoplasmic reticulum in skeletal muscle fibers. This mechanism remains to be elucidated; however, phenol may prove to be a new agent used to study skeletal muscle function.Supported by NIH grant 1P01HL091830‐01A18101