EFFECT OF NICOTINE ON SPINAL SYNAPTIC CONDUCTION AND ON POLARISATION OF SPINAL CORD

Abstract

The influence of nicotine on C.N.S. was investigated by means of 3 different types of expt.: a) recording of the polarization state of the spinal cord, b) mechanical recording of the knee-jerk and flexion reflex, and, c) recording of the reflex action potentials. The asphyxial depolarization, achieved by interrupting the aortic flow above the celiac artery was unaltered in the presence of nicotine. The knee-jerk and flexion reflexes were depressed by small doses of the drug (5 mg./kg.), the former (monosynaptic) reflex being inhibited to a greater extent than the latter (multisynaptic) response. The flexion reflex was abolished by the admn. of moderate doses of nicotine (20 mg./kg.). This was shown to be due to the peripheral curarizing action of the drug. The effects of nicotine on reflex action potentials led off from the ventral roots of L7 or S1 were in accord with the findings observed in the previous expt.: monosynaptic activity was depressed by low concns. while only a slight depression of the multisynaptic activity was observed. Potentiated action potentials were observed when doses of nicotine amounting to 100-200 mg./-kg. were administered.