THE EFFECT OF ESERINE ON SPINAL REFLEXES IN THE DOG

Abstract

Eserine, (0.025-0.2%) was perfused under constant pressure and temp. through the lumbar subarachnoid space of the barbitalized or chloralosed dog, with, and without, the spinal cord sectioned at T 10. The flexion reflex, knee jerk, and crossed extension reflex of the quadriceps were observed. The knee jerk was consistently depressed, whereas the crossed extension reflex of the same limb, and the flexion reflex of the opposite limb were augmented. Intravenous eserine gave essentially the same results, except for the knee jerk of the chloralosed dog, which was depressed in about 55%, and augmented in 45% of the observations. The results were independent of changes in blood pressure, for atropinization did not abolish the effects on the reflexes. The site of action was not in the muscle or neuromuscular junction, as shown by simultaneous observations of the response of the muscle to stimulation of its motor nerve. Eserine evidently acted directly on the spinal cord, and the inhibition of the knee jerk and augmentation of the other reflexes was due to an action in the intemuncial portions of the reflex arcs.