Tetanus and Hyperresponsiveness of the Mammalian Spinal Cord Produced by Strychnine, Guanidine and Cold

Abstract

Tetanus and hyperresponsive states produced by 3 means were studied in cats'' spinal cord. Strychnine first produced a depolarization of motoneuron pool which caused i very regular rhythmic discharge in ventral root accompanied by slow waves in the dorsal roots capped by asynchronous anti-dromic discharges. The rhythm of tetanus recorded from ventral roots at various levels of spinal cord was synchronous and was disturbed or reset by an activation of polysynaptic reflex pathways, but not by monosynaptic reflexes or antidromic stimulation of ventral roots. Guanidine first caused an augmentation of both ventral and dorsal root reflexes, then spontaneous antidromic discharges in dorsal root unaccompanied by ventral root firing. Later the ventral roots also showed a spontaneous activity and antidromic potentials produced by stimulation of ventral roots were similarly augmented. Rate of guanidine tetanus was slow and irregular. Cooling the spinal cord to a critical temperature produced repetitive firing in ventral and dorsal roots which was not well synchronized and eventually the irregular spontaneous discharges occurred. Evidence was obtained that the tetanic activities caused by these means originated within the cord itself.