Inhibitory Action of Bulbar and Suprabulbar Reticular Formation on the Spinal Reflex Pathway

¹ From the Department of Physiology, State University of New York, College of Medicine at New York City, Brooklyn, New York

Inhibitory action of bulbar and suprabulbar reticular formation on spinal flexor and extensor reflex pathways was studied. In some instances a reciprocal effect was obtained but usually a generalized inhibition resulted. Inhibition varied in magnitude but was always present during reticular formation stimulation. In a high percentage of cases inhibition persisted for a period of 2–3 minutes after cessation of stimulation. Stimulations which blocked the reflex occasionally also had an inhibitory effect on the antidromic potential evoked by stimulation of the motor fibers involved in the reflex but in many instances the antidromic potential was actually augmented. The inhibitory stimulation also did not prevent facilitation of the antidromic potential by orthodromic stimuli. Post-tetanic potentiation was not prevented nor terminated by stimulation of the inhibitory areas of the reticular formation. This data suggest that inhibition from the reticular formation does not block afferent terminals but acts postsynaptically in such a manner, however, as not to increase axon hillock block of antidromic invasion of the soma. Effects of certain anesthetics and drugs on these phenomena were studied.