The use of chronic polyelectromyography in neurophysiological and behavioural experiments

A method of electromyography (EMG) recording is described which makes it possible to follow simultaneously the activity of 4 muscles in awake, unrestrained rats and cats for 3-5 months. The implantable recording array consists of a percutaneous connector, steel wire spiral leads contained in silicone tubing and bipolar platinum electrodes embedded in silicone platelets. These electrode probes can be fixed onto the surface of various muscles without direct injury to the muscle and, at the same time, without electrical interference from neighbouring muscles. In most rats, EMG activity was recorded bilaterally from the soleus and tibialis anterior muscles. This method has so far been employed for assessing the muscle activity in experiments on reflex muscle atrophy, unilateral hindlimb deafferentation, disuse muscle atrophy induced by limb immobilization and compensatory muscle hypertrophy. A simple computer program has been used to evaluate the resting, postural activity. Objective information about muscle coordination, patterns of locomotor and reflex activity, muscle use and disuse under specific experimental conditions can only be obtained in awake, unrestrained laboratory animals by recording electromyographic (EMG) activity in chronic experiments. For this purpose we developed a method of chronic polyelectromyography allowing recording from 4 muscles in rats and cats (Hník et al. 1978) for several months. The method is briefly reviewed here, together with some applications to animal experiments.