[Changes in the ionic mechanisms of the electro-excitability of the somatic membrane of rat sensory neurons during ontogenesis. Distribution of ion channels of the inward current].

Distribution of different types of ionic channels carrying inward currents was studied in the somatic membrane of rat dorsal root ganglion neurons within three age groups: 5-9 days, 45 days and 90 postnatally. The number of neurons whose membrane contained simultaneously four types of inward current channels ("fast" tetrodotoxin-sensitive and "slow" tetrodotoxin-resistant sodium low- and high-threshold calcium one's) was progressively reduced in successive groups. The first group contained 14.5%, the second 5% and the third group 1% of such neurons. These changes were due to disappearance of "slow" sodium and low-threshold calcium channels from the membrane; the number of neurons whose somatic membrane contained only two types of inward current channels ("fast" sodium and high-threshold calcium) has increased, respectively.