Magnesium sulfate suppresses electroencephalographic manifestations of CNS oxygen toxicity.

We studied the effects of parenteral magnesium sulfate (MgSO4) administration on electroencephalographic seizures induced by hyperbaric oxygen (HBO) in awake rats. Sixteen rats chronically implanted with electrocorticographic electrodes were preinjected i.p. with either vehicle or 3 mmol/kg MgSO4 (the latter resulted in serum levels of 3.5-5.5 mmol/liter) and then exposed to 6 ATA O2 in a pressure chamber. The time to develop an electric ichtal seizure was measured and compared to that in the same animal receiving the alternate treatment 3 days later. Mean and median times after the magnesium treatment were almost double those of vehicle administration. A central anticonvulsive action of magnesium, which should be investigated over the entire HBO range, is indicated.