RU2107507C1 - Method to stimulate nerves - Google Patents

Abstract

FIELD: experimental medicine, neurophysiology, neurosurgery. SUBSTANCE: scorpion's toxin is applied as a stimulator at the dose of 0.1.0 microgram to be then introduced as a microinjection under epineurium followed by visual inspection of fibrillation of stimulated muscle or registration of its electromyogram. EFFECT: higher efficiency to conduct local stimulation of anatomically not easily accessible nervous structures. 2 cl, 4 dwg

Description

 The invention relates to experimental medicine, namely to neurophysiology and neurosurgery and can be used for local stimulation of nerve trunks and plexuses.

 The well-known "Method of subcutaneous stimulation of nerves or local destruction of tissues" according to US Pat. US N 4343301, in accordance with which the stimulation is carried out using low-frequency sound vibrations. However, this method requires special equipment, converters and does not provide local effects, for example, with intra-beam stimulation of the nerve trunk.

 There is also known a method of chemical stimulation of an isolated nerve of a frog by changing the chemical composition of the external environment. (See the Guide to physiology. - M.: Science, 1975, p. 227 - 228). This method is of little use in a holistic organism, and especially in anatomically inaccessible places, because it requires the complete isolation of a nerve section, sufficient in length to be placed in a special chamber with a solution of variable composition.

 Closest to the proposed is a method of chemical stimulation of neurons described in article A.A. Aleksandrova et al. “The effect of intracortical chemical stimulation on the background activity of neurons of the sensorimotor cortex of the brain of a cat” (see Neurophysiology, 1982, vol. 14, No. 4, pp. 347–352).

 This method is carried out by microionophoresis of glutamate into neurons of the cerebral cortex. However, this method is technically complicated, requires the manufacture of special microelectrodes, an electronic injector, and it is practically difficult to perform during chemostimulation of the nerve plexuses. In addition, glutamate does not have a stimulating effect on the peripheral nerves.

 The purpose of the invention is the implementation of effective local stimulation of anatomically difficult to reach nerve structures.

 This goal is achieved by the fact that a scorpion toxin is used as a stimulant in doses of 0.1 - 1.0 μg in a volume of 5 - 10 μl of physiological saline, which is administered by microinjection under epineuria followed by visual observation of fibrillation of the muscle stimulated by this nervous structure or recording it electromyograms.

 In FIG. 1A, an electromyogram of rat gastrocnemius muscle is given in response to the introduction (indicated by an arrow) of the scorpion toxin (1) and physiological saline (2) and dynamics (Fig. 1B) of EMG amplitude into the tibial nerve after a single injection of the toxin; in FIG. 2 - antidote effect of novocaine, which removes the stimulating effect of the toxin; in FIG. 3 - dose-dependent nature of the stimulating effect of the toxin; in FIG. 4 - action potentials of the gastrocnemius muscle and its EMS before and after administration of the toxin and physiological saline, illustrating the harmlessness of the used dose of the toxin.

The method is as follows. Under general anesthesia in an animal (rat, cat, etc.), the studied nerve plexus (brachial, lumbar, etc.) is exposed operatively by way of a toxin solution at the rate of 0.2 μg of toxin per 10 μl of physiological saline. The prepared solution is drawn into a syringe for microinjection. connected with a flexible hose to an injection needle, subepineurally insert the needle into the studied branch of the nerve plexus and inject the toxin solution. Due to the flexible joint of the needle and syringe, it is possible to introduce a chemical stimulant into the anatomically inaccessible zone, for example, the brachial or lumbar plexus. Next, visual observation of fibrillation of the corresponding muscle or registration of its electromyogram is carried out, moreover, muscle fibrillation or an increase in the EMG amplitude is observed 5-10 seconds after injection for 15-20 minutes (see Fig. 1A), which indicates that the stimulating nerve bundle innervates this muscle. For comparison: mechanical irritation of a nerve with the volume of injected saline solution (10 μl) has practically no stimulating effect (Fig. 1A). To stop the stimulating effect of the toxin at the height of its effect, a 0.5% solution of novocaine is injected into the nerve plexus branch or nerve trunk and a blocking effect is obtained almost instantly (see Fig. 2)
The stimulating effect of the toxin on the nerve depends on the dose and is characterized by a linear relationship in the range of 0.1 - 1.0 μg (see Fig. 3). Doses smaller than 0.1 μg are ineffective, the effect of doses greater than 1.0 μg is characterized by saturation and, therefore, their use is inappropriate.

The locality of the toxin exposure is completely determined by its primary depot at the injection site and is due to the high selectivity of binding to the membrane of nerve fibers. This is proved by the pharmacokinetics of labeled ¹²⁵ 1 toxin: half-life t $\genfrac{}{}{0ex}{}{\text{β}}{}$$\genfrac{}{}{0ex}{}{}{\text{1/2}}$ = 2.7 • 10 ³ min, half-life t $\genfrac{}{}{0ex}{}{\text{α}}{}$$\genfrac{}{}{0ex}{}{}{\text{1/2}}$ = 2.5 minutes Thus, the toxin is completely localized at the injection site.

 The harmlessness of the toxin is proved by the reversibility of its effect, estimated by the preservation of nerve conduction after subepineural administration of the maximum of the doses used. This is well illustrated in FIG. 4, where 1A is the background PD of the muscle with a single irritation of the nerve, 1B is the EMG of the muscle after injecting physiological solution into the nerve, 2A is the background PD of the muscle, 2B is EMG 1 min after the injection of 1 μg of toxin into the nerve, 3A is the PD of the muscle after 15 min after the introduction of the toxin, 3B - PD muscle 25 minutes after the introduction of the toxin. Calibration for PD: amplitude 1 mV, duration 10 ms, for EMS: amplitude 100 μV, duration 200 ms.

The average lethal dose (DL ₅₀ ) of the toxin for rats was 1 mg / kg or 0.2 mg (200 μg) per animal weighing 200 g. Thus, the highest dose administered to the nerve - 1 μg is 1/200 of the DL ₅₀ and is not toxic.

 The method of nerve stimulation using scorpion toxin is characterized by ease of implementation, the possibility of local exposure in anatomically difficult to reach tissues and organs, harmlessness, easy dosage and the presence of a specific antidote in case of an overdose and the need to terminate novocaine. In the implementation of the method, preliminary isolation of the stimulated structure from the body is not required, and it can be used to create local foci of excitation in a working organ, for example, a heart or muscle.

Claims (2)

 1. A method of stimulating nerves in a chemical way, characterized in that subepineural microinjection of scorpion toxin into the nervous structure is carried out, followed by visual observation, fibrillation of the muscle stimulated by this nerve structure or recording of its electromyogram.  2. The method according to claim 1, characterized in that the scorpion toxin is administered in an amount of 0.1 - 1.0 μg in a volume of 5.0 - 10.0 μl of physiological saline.

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