Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

Abstract

Denervated frog's semitendinosus muscles were studied. Fibrillation potentials generate propagated spikes which are conducted at a rate similar to that calculated for innervated muscles. The twitch tension per unit area was similar in denervated and innervated single fibres; the average value corresponded with values reported in the literature for fibres stimulated at 125/sec. Manganese ions (1-3 mM), selectively inhibit fibrillation potentials and have no appreciable effect upon evoked spikes. Mn2+ also inhibits (40-50%) the twitch responses and abolishes the resting tension of muscle fibres. The latter effects were observed in denervated as well as in innervated preparations when the fibres studied belonged to fascicles located at the site of entrance of the nerve. Disruption of the transverse tubular system by glycerol treatment does not interfere with the generation of fibrillation potentials, although the effects on twitching are similar to those reported in the literature. A possible mechanism is proposed to explain the generation of fibrillation potentials in frog denervated muscles.The fibrillatory activity of the denervated semitendinosus muscle of the frog has been described in a previous paper (LOPEZ, 1978). It was mentioned, as a possibility to explain the poor tension development occasionally observed in that study, that fibrillation potentials might not give rise to propagated electrical activity. It was also considered that the transverse tubular system (TTS), a possible site of origin of the discrete depolarizations found in denervated mammalian muscles (PURVES and SAKMANN, 1974;SMITH and THESLEFF, 1976), could provide an explanation to the fact that, in the frog, it is possible to obtain spontaneous depolarizations, and repetitive firing, from any spot along the muscle length.On these bases, the present study was aimed at obtaining further information related to the propagation of fibrillation potentials and inquiring further about the role the TTS may possibly play in the genesis of the electrical fibrillatory activity. The results obtained during the study are described in this paper.

Post-tetanic potentiation and inhibition in single fibres isolated from frog semitendinosus muscle.

“…Single twitch fibres (N=115) were dissected out from the ventral head of semitendinosus muscles. The denervation procedure and the general technique followed in this study were as described previously (LOPEZ, 1979). The left muscle was denervated in each animal.…”