[Effect of magnesium ions on presynaptic inhibition of monosynaptic reflexes]

In experiments on spinal narcotized cats perfusion of lumbosacral spinal cord through central canal with artificial cerebrospinal fluid containing high concentration (20-46 mM) of magnesium ions led to reversible depression of negative DRP as well as to depression of prolonged "presynaptic" inhibition of extensor monosynaptic reflexes produced by repetitive impulse volleys in group I flexor muscle afferents. Magnesium did not cause a depression of monosynaptic reflex discharges in spinal ventral roots.