Electrophysiological identification of pontomedullary reticular neurons directly projecting into dorsal column nuclei

In cats 'encephale isole', cerebellectomized and curarized, neurons projecting from the bulbopontine reticular formation to the cuneate nucleus were identified by stimulating their axons in this nucleus by means of Eide micropipettes and by recording both field potential and antidromic responses from single somata in the nucleus gigantocellularis. Of 130 neurons responsive to cuneate stimulation, 17 (12%) were found that were antidromically activated. The small proportion of antidromic responses might reflect the small size of the projection pathway. However, there are reasons to believe that a certain number of neurons might have been missed because of biasing factors introduced by the microstimulation technique. Neurons that were activated orthodromically were also observed, responding after latencies spread over rather wide ranges. The possible pathways for this activation are discussed.