ROLE OF WDR NEURONS IN A HIND-LIMB NOXIOUS HEAT EVOKED FLEXION WITHDRAWAL REFLEX

Behavioral experiments and neurophysiological experiments, the two maj or types of preclinical studies which have paved the way for the devel opment of spinal analgesia were compared under identical conditions ut ilizing the same animals. The results demonstrate that the activation of the wide dynamic range (WDR) neurons preceded the behavioral withdr awal reflexes, and that the activation of the WDR neurons occurred at lower stimulus temperature than that for the withdrawal reflex. The re sults suggest that the neuronal activation began before the behavioral reflex but also that the firing frequency of the WDR neurons at the t ime of the withdrawal reflex could not distinguish between non-noxious and noxious stimuli. Further study is needed to elucidate the neurona l mechanisms of the activation of the behavioral reflex.