[Evoked potentials of the somatic cortex, thalamus, and electromyographic reactions of the cat shoulder muscles elicited by elbow joint straightening in norm and after injection of neurotoxin].

EMG activity from the elbow joint muscles and evoked potentials (ep) from the somatic cortex (fields 4, 6) and thalamic nuclei (vl, vpl) elicited by passive extension were recorded in the unanesthetized cats before and after MPTP injection (total dose 10 mg/kg). It was shown, that after MPTP injection changes of the EMG response in cats are similar to that observed in parkinsonian patients: The increase of amplitude and duration of the stretch-related m2-3 -components of EMG, as well as excitation increase in thalamus and cortex was shown after MPTP. Perturbation of an external extensor loading applied to the forearm with different fixed force moments elicited m. biceps brachii EMG reactions which amplitude in norm correlated with a muscle stretch size. The MPTP injection influenced this dependence. Contrary to EMG responses n26-60 amplitude of the thalamic and cortical EP did not depend on the level of muscle stretch neither in norm nor after MPTP injection. Hence it supposed that an afferent excitation, which was responsible for this EP, did not take part in a generation of the m2-components of the stretch reflex. Late (n100) component's amplitude of the thalamic nuclei EP depended on the muscle stretch level. After MPTP injection this relation disappeared just as in the EMG responses. Since m2 components aroused in the spinal cord motor neurons earlier than n100 components in thalamus it is supposed that excitation of shoulder muscle receptors and spinal neurons, which provided with origin of m2 components consisting of EMG responses, were responsible for generation of the EP late components of thalamic nuclei VL and VPL.