EFFECTS OF ANTIDROMIC CONDITIONING ON SOME MOTONEURONS AND INTERNEURONS

Abstract

The effects of antidromic stimulation of motor nerves on some motoneurons and interneurons have been studied in experiments utilizing intracellular recording from the spinal cord of acute decapitate cats. A high proportion of the motoneurons studied had a monosynaptic firing probability of 100, suggesting that penetration of a cell by a microelectrode may modify the unit''s excitability even though no overt sign of injury is present. With the use of several criteria, it was found that recurrent facilitation was widespread among the individual cells of facilitated nuclei. Within these nuclei facilitation is just as likely to be found in tonic as in phasic motoneurons; facilitation may be found more frequently among flexor cells that fire repetitively than among those that do not. Interneurons whose firing was inhibited by antidromic stimulation of muscle nerves were observed. The duration of this inhibition is similar to that of recurrent facilitation and it is suggested that some of these cells are involved in the pathway for recurrent facilitation.