[Electrical activity of motor neurons of the vascularly perfused spinal cord of kittens].

In 5--22-day kittens, using an original method of perfusion of the spinal cord and the hindlimb through arterial vessels, PSPs were intracellularly recorded from lumbar motoneurons of perfused cord during stimulation of dorsal roots, ventral columns or muscle nerves of the hindlimb. All synaptic actions were completely though reversibly abolished in Ca2+-free solution containing 1.5--2.0 mM Mn2+, indicating the chemical mode of transmission in these synapses. The addition of Mn2+ and removal of Ca2+ markedly reduced and eventually abolished the post--spike after--hyperpolarization of motoneurons without alteration of the spike height. In motoneurons the input resistance ranged from 1.3 to 15.1 Mom (5.9 Mon on the average).