[The early postdenervation changes in the properties of the postsynaptic membrane of amphibian muscle fiber].

The amplitude-temporal characteristics of miniature end-plate currents (MEPC) were studied in denervated frog cutaneous-pectoral muscles. After the nerve cutting, the initial shortening of MEPC decay time was followed by its prolongation. In 6-8 days after the denervation, the MEPC sensitivity to membrane potential decreased, while the average open time of ACh-activated channels increased 2-fold. The autocorrelation function of ACh-induced current noise revealed two components at some of the synapses. The denervation of the frog cutaneous-pectoral muscle seems to make the postsynaptic membrane to contain two types of ACh receptors (AChR): normal synaptic AChR which gradually disappear, and new synthesized AChRs which open the channels with much longer mean time and a lesser sensitivity to membrane potential changes.