| Abstract: | Postsynaptic responses evoked by stimulation of the descending tract and dorsal roots were investigated by means of intracellular microelectrodes in experiments on preparation of the isolated lamprey spinal cord. Besides giant reticulospinal (Mullerian) axons, a broad spectrum of descending fibers and dorsal-root afferents were shown to form synaptic inputs with both chemical and electrical mechanisms of transmission with motoneurons, as revealed by the sensitivity of the corresponding PSPs to absence of calcium ions and excess of magnesium ions in the external medium. During combined stimulation electrotonic PSPs may have a rapid temporal course characteristic of elementary responses, but they may also lead to smooth and slow depolarization of the postsynaptic membrane, evidence that they may perform not only a mediator but also an integrative function.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 512–517, September–October, 1977. |
