EFFECTS OF STRYCHNINE UPON SUPRASPINAL INHIBITION

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Abstract
Effects of strychnine upon the pontine reticular inhibition to lumbar extensor motoneurons were examined by using the monosynaptic reflex test as well as the intra-cellular potential recording from motoneurons of the cat. The inhibition elicited by single pulse stimulation of the pontine reticular formation was eliminated by strychnization in the same dosis with that for blocking the direct inhibition. The elimination of inhibiton usually made the facilitatory component, having been hidden by the inhibition, predominant. Under heavy strychnization which evoked strychnine tetanus, it was observed on ventral root and intracellular potentials that, when repetitive stimulation of the pontine reticular formation was applied with appropriate strength and frequency, the strychnine tetanus could be completely stopped during the stimulation. The appropriate parameters of stimulation were those for eliciting the sufficient and continuous smooth depolarization in motoneurons. The mechanism of stopping the strychnine tetanus was discussed in concern with the accommodation of motoneurons to the elicited sustained depolarization.