[Central Pattern Generators: Mechanisms of the Activity and Their Role in the Control of "Automatic" Movements].

Central pattern generators (CPGs) are a set of interconnected neurons capable of generating a basic pattern of motor output underlying "automatic" movements (breathing, locomotion, chewing, swallowing, and so on) in the absence of afferent signals from the executive motor apparatus. They can be divided into the constitutive CPGs active throughout the entire lifetime (respiratory CPGs) and conditional CPGs controlling episodic movements (locomotion, chewing, swallowing, and others). Since a motor output of CPGs is determined by their internal organization, the activities of the conditional CPGs are initiated by simple commands coming from higher centers.

Motor reactions during the antenatal period correlated with the periodic change in the activity of the cardiovascular system.

A connection between the periodic appearance of vagal bradycardia and of intrauterine large-amplitude respiratory movements, as well as the appearance of generalized jerky-type and more sustained extensor motor reactions, has been established in experiments on dog fetuses connected with the mother through the umbilical cord. Brief vagal bradycardia also arises immediately after completion of these reactions and is an analogue of the vagal phase in adults after motor activity. These correlated phenomena are caused by periodic reversible mild hypoxemia which through the chemoreceptors of the sinocarotid zone stimulates the centers of vagal innervation of the heart and the centers of innervation of skeletal muscles.

Comparative ontogenetic features of skeletal muscles in physiologically mature and immature mammals.

One series of experiments investigated the time required by such indices of the states of skeletal muscles as membrane potential (MP), action potential (AP), and content of total protein and dense residue to acquire values approximating those found in adults. We established that these indices acquire values approximating those found in adults at the beginning of sexual maturation in both rats and dogs. Chronologically, these values require one-fifth the time to become established in rats as they do in dogs.