Recovery from experimental paraplegia after levodopa administration.

In decompression sickness and during some surgical procedures, air emboli that form sometimes cause serious damage if the gas bubbles find their way to the vital organs. Paralysis of the spinal cord is one of the most serious manifestations induced by air emboli. Exposure to compression chambers is effective in air emboli treatment, but availability of chambers is inadequate and the treatment is lengthy. Until now there has been no fully effective injectable agent that can remedy the damage caused by air embolization. In this work levodopa was chosen as an injectable drug that might help to improve recovery from experimental paraplegia because of the reported effects of levodopa on muscle tone, spasticity and locomotion. To induce air emboli, the descending aorta of rats was chronically cannulated. Two weeks later, after full recovery from surgery, air was injected through the chronically implanted cannula into unanesthetized rats (0.35 ml of air per 100 g, during 4 sec). The paraplegia (paralysis of both hind legs) was manifested 2-10 minutes later. Only animals that had total paraplegia, without any sensation, were used in the experiments. Levodopa was administered 2 minutes after paraplegia was established. The levodopa treatment was repeated each day during one week. After six days, ten levodopa treated (intra-arterially) animals in a group of twelve and six levodopa treated (intraperitoneally) animals in a group of eight recovered completely from paraplegia. In control groups only three from thirteen (untreated), or two from twelve (solvent administration) animals recovered from paraplegia.