Effect of spinal cord transection on neuromuscular function in the rat.

The effect of T6 spinal cord transection on neuromuscular physiology, pharmacology, and histochemistry as well as succinylcholine-induced changes in serum potassium were studied in 88 Sprague-Dawley rats and compared to 19 control animals. Resting membrane potential of spinal cord transected animals decreased by a maximum of 15 mV. This change was significant at days 3, 7, and 30 posttransection. Cell membrane input resistance was significantly decreased at posttransection days 10 and 15. Succinylcholine-induced contracture increased 3- to 4-fold and was significantly greater than control values on days 5 and 10 posttransection. Concomitant with the development of contracture there was a spread of cholinergic receptor from the end plate region. This differed from control acetylcholine sensitivity on days 7, 15, and 30 when receptor could be detected in excess of 1000 micrometer from the endplate. Serum K+ levels 3 min after administration of succinylcholine (1 mg/kg) was significantly elevated on days 10 and 30. Spinal cord transection causes denervation-like changes in the involved skeletal muscle.