| Abstract: | ![]()
In old rats the mean membrane potential (MP) was shown not to differ significantly from the mean value of this parameter in young sexually mature rats (56.5±1.26 and 58.4±1.4 mV respectively), but at the same time the frequency of detection of motoneurons with MP of 70 mV or more was 18.6% lower in the old than in the young animals, and the frequency of motoneurons with MP of 50–59 mV was 14.2% higher. Thresholds of direct excitability in the old rats were lower in the old rats than in young sexually mature animals [(2.0±0.2)×10–9 A compared with (3.0±0.3)10–9A]. The number of discharges during polarization of the neuron for 50 msec reached 4–5, which corresponds to 80–100 spikes/sec. The frequency of action potentials (AP) determined for the first two intervals, reached 125/sec, compared with over 300/sec in young, sexually mature rats. The duration of the antidromic spike was increased (1.02±0.09 msec in young sexually mature animals, 1.65±0.14 msec in the old rats; P<0.001). Antidromic spikes from motoneurons of old rats as a rule had no late depolarization.Laboratory of Physiology, Institute of Gerontology, Academy of Medical Sciences of the USSR, Kiev. (Presented by Academician of the Academy of Medical Sciences of the USSR D. F. Chebotarev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 8, pp. 911–913, August, 1976. |
