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Electrical potential measurements of membrane resting and action potentials were made by means of electrolyte-filled glass micro-electrodes on single fibres of the musculus gracilis of the cat using a perfused hind-limb preparation in situ. The release of potassium from muscle and the tension developed by the gastrocnemius muscle were simultaneously recorded. The normal resting potential in our series was 91.7 mV (s.d. ± 6.7 mV). Partial replacement of the chloride by sulfate in the perfusion fluid led to (a) potassium release from the perfused hind-limb, (b) reversible contracture of the gastrocnemius muscle, (c) depression of the membrane resting potential which was proportional to the degree of replacement of chloride by sulfate in the perfusion fluid and (d) to the occurrence of volleys of spontaneous fibrillation potentials some of which had the shape of damped oscillations. These findings are similar to those observed after treatment with veratrine and are interpreted to be due to (1) increase in sodium permeability and (2) disturbance of the Donnan equilibrium for chloride ions. [ABSTRACT FROM AUTHOR]

The release of potassium ions from striated muscle, and the changes in mechanical tension developed by the gastrocnemius muscle on intraarterial injection of ACh, were investigated by isolated perfusion of the hind limbs in cats. The reaction of the normal innervated and chronically denervated muscle in the same animal were compared before and during perfusion with 2·10 M/l desoxycorticosterone glucoside (DCG). The following results were obtained: after perfusion with DCG no change in the spontaneous release of potassium ions occurred neither on the innervated nor on the denervated muscle. The potassium release following intra-arterial injections of various doses of ACh was significantly reduced on innervated and denervated muscle. On the denervated muscle there was also a considerable reduction of the height of contractures caused by ACh administration. The results make it probable that DCG acts by an inhibition of depolarisation in the same way as d-tubocurarine. [ABSTRACT FROM AUTHOR]

Both hind limbs of cats (one being normally innervated, the other 8-12 days after denervation) were perfused and the quantities of potassium liberated from the two limbs in response to intraarterial injections of varying amounts of acetylcholine were compared by collecting the venous outflow from both sides separately; considerably larger quantities of potassium were found to be liberated from the denervated than from the innervated muscle after equal doses of ACH; the threshold dose of ACH for eliciting a measurable liberation of potassium being much lower on the denervated side. The dose response relation between injected ACH and potassium-liberation is of a different nature for innervated and denervated muscle. The results obtained are compatible with expectations derived from the 'short circuit theory' of the transmitter action on the neuromuscular endplate ( Fatt and Katz). The reasons of the difference in the dose relations for the innervated and denervated muscle are discussed. [ABSTRACT FROM AUTHOR]