Magnesium chloride injected into rat rostral neostriatum before picrotoxin prevents motor hyperactivity induced by this GABAA receptor antagonist: prevents the increase in spontaneous motor activity in the open field test and reduces reproduction and duration of choreic hyperkinesia. Injection of magnesium 15 min after picrotoxin virtually did not modify the hyperkinetic effects of picrotoxin. The results indicate the role of calcium processes in the appearance of strial picrotoxin hyperactivity and principal possibility of its correction with magnesium only before the cascade of respective calcium ionic transformations is triggered in the brain.