| Abstract: | Experiments on anesthetized and immobilized cats showed that repeated antidromic discharges can be evoked in 32.5% of sympathetic preganglionic neurons of the lateral horns in segments T3, T8–9, and L2 of the spinal cord, with intervals of 16 msec or more between them, which is much greater than the refractory period of these neurons. This feature was shown not to be connected with the properties of axons of that group of neurons and, in particular, with their after-subnormality. After orthodromic discharges in neurons of this group, for a much longer period of time than could be accounted for by possible collision, no antidromic discharges likewise were evoked. As a result of antidromic activation of some of these neurons in one segment, definite inhibition of the orthodromic response of other neurons of the same segment appeared, etiher by a reflex mechanism or through stimulation of descending pathways. The results point definitely to the existence of a mechanism of recurrent inhibition in some sympathetic preganglionic neurons of the lateral horns.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 382–389, July–August, 1977. |
