[Separation of undamaged single nerve fibers by using an ultrasonic microscalpel].

A routine procedure for dissection of single nerve fibres with sharpened sewing needles is rather tiresome and occasionally traumatic because of poor efficiency in cutting interfibrous connective tissue and sticking out patches of it to preparative needles. The described method using microscalpel oscillating with ultrasonic frequency is free from these shortcomings. Voltage clamp tests proved an innocuous character of this method for excitable nodal membrane.

[Localization of the binding site for quaternary derivatives of ajmaline in the Na channel of an excitable membrane].

The effects of external or internal application of quaternary derivatives of ajmaline and N-propyl ajmaline (NMA) to the frog nodes of Ranvier were studied by the voltage clamp method. It was established that external application of NMA is much less effective than that of the tertiary amine ajmaline or its quaternary analog N-ethyl ajmaline at comparable concentration. Even at a concentration of 1 mM NMA when applied externally caused only relatively insignificant tonic and use-dependent inhibition of sodium currents.

[Differences in the action of Ca2+ ions on a cumulative Na-channel blockade due to tertiary and quaternary amines].

In voltage-clamp experiments on frog myelinated fibres it has been established that the increase in Ca2+ concentration from 2 to 20 mM does not effect the use-dependent (cumulative) inhibition of sodium channels (INa) produced by the tertiary local anesthetics (lidocaine, tetracaine, etidocaine) and the quaternary antiarrhythmic drug N-propyl ajmaline (NPA). The NPA-induced inhibition of sodium channels does not undergo any essential changes as the (Ca)0 is raised from 2 to 20 mM. On the contrary, the cumulative blockade produced by the tertiary local anesthetics under such an elevation of the (Ca)0 is sharply reduced.

[Differences in the blocking action of benzocaine and amino compounds on batrachotoxin-modified node of Ranvier sodium channels].

Voltage-clamp experiments on the frog Ranvier node have shown that batrachotoxin (BTX) decreases drastically the sensitivity of sodium channels to the blocking action of various tertiary (procaine, trimecaine, ajmalin, strychnine) and quaternary (QX-572, N-propylajmaline) amine drugs but does not affect noticeably sodium channels blockade produced by neutral benzocaine. The inhibition of BTX-modified sodium current by large concentrations of trimecaine (3.5 mM) is time- and voltage-dependent.

[Stimulus dependent sodium channel blockade in node of Ranvier membranes by the quaternary antiarrhythmic N-propyl ajmaline (neogiluritmal)].

The blocking action of neo-gilurytmal (NG), a quaternary derivative of aimalin, on sodium channels was studied in the voltage-clamped node of Ranvier. NG exerted no action on the resting membrane unless the repetitive pulsing was turned on. A series of repetitive depolarizing pulses of short duration (5 ms) produced the accumulating "stimulus-dependent" blockade of sodium channels.