Fusimotor Outflow to Pretibial Flexors During Isometric and Isotonic Fatiguing Contraction of Triceps in Decerebrate Cats

Abstract

It has been shown that changes in discharge rate occur in fusimotor neurones to a muscle during fatiguing contractions of it or its close synergists during long-lasting isometric (Ljubisavljevic, Jovanovic & Anastasijevic, 1992a) and isotonic contractions (Ljubisavljevic & Anastasijevic, this volume). Effects are also seen in fusimotor neurones to a remote, partly synergistic non-contracting muscle group (Ljubisavljevic, Jovanovic & Anastasijevic, 1992b). These effects seem to be due to both mechanosensitive and chemosensitive small-diameter muscle afferents. These same muscle afferents can be expected to exert reflex effects also on fusimotor neurones to pretibial flexors (Appelberg, Hulliger, Johansson & Sojka, 1983a, b). Since the signals from muscle spindles in antagonist muscles may be as important for the control of movements as those from the agonist muscles, it seemed to us of interest to look for the changes in discharge rate of fusimotor neurones to pretibial flexors, acting primarily as antagonists to the triceps surae muscles, during long-lasting isometric and/or isotonic contractions of the latter.