[Focal spinal cord potentials in the postnatal ontogeny of the rat].

Single stimulation of n. tibialis in rat puppies during the first month of their postnatal life more than 4-fold increases the amplitude of the negative deflection of the cord dorsum potential and almost 2.5 times decreases its duration. Due to a significant increase in the conduction velocity along the fastest afferents, the latent period decreases approximately by 6 times. In newborn rats, gradual pattern of the reaction to the increasing stimulation is manifested rather poorly. Focal potentials recorded during the impalement of microelectrode into the dorsal part of the spinal cord, include a complex of negative deflections of one pre- and three postsynaptic components which differ with respect to their latent periods, maximum localization and relation to the strength of a stimulus. These components are differentiated quite well already to the end of the second week of postnatal life. During the first week, focal potentials exhibit long latent periods of maxima and low amplitude.