TONE AND TENDON REFLEXES AFTER ASPHYXIATION OF THE SPINAL CORD

Abstract

Five-15 mins. after the end of a 15-65 min. asphyxiation of the spinal cord, a slight extensor tone developed which, after reaching a maximum, disappeared within 30 mins. after asphyxiation (initial tone). This tone was followed by a period in which neither tone nor other forms of reflex activity were present (period of areflexia). Extensor tone could be elicited during this period by renewed asphyxiation of the cord. In the 65 and 55 min. expts., a high extensor tone developed after the period of areflexia. This secondary tone was temporary and disappeared after a few hrs. In the 45 and 35 min. expts., tendon reflexes developed after the period of areflexia, followed by secondary tone. The secondary tone was usually temporary in these expts. also, but sometimes remained for the rest of the animal''s life. In the 25 and 15 min. expts., the period of areflexia was followed by the development of tendon reflexes and usually the return to normal reflex excitability. It has been possible to prove the reflex nature of initial and secondary tone and of the extensor tone elicited during the period of areflexia by renewed asphyxiation of the cord.