Behavioral evaluation of the anti-excitotoxic properties of MK-801: comparison with neurochemical measurements.

The ability of MK-801 to protect striatal neurons from the excitotoxic action of quinolinic acid was evaluated by means of apomorphine-induced rotational behavior and by measurement of striatal choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) activity, neurochemical markers for cholinergic and GABAergic neurons, respectively. Animals with a unilateral quinolinic acid lesion of the striatum exhibited a vigorous rotational response when challenged with apomorphine (0.5 mg/kg, s.c.) 6 days later and were found to have an 88 90% depletion of striatal ChAT and GAD activity. Treatment with a high dose of MK-801 (10 mg/kg, i.p.) prior to intrastriatal injection of quinolinic acid eliminated the subsequent rotational response to apomorphine and resulted in complete protection of striatal ChAT and GAD activity. Lower doses of MK-801 (1, 3 and 5 mg/kg, i.p.) failed to significantly reduce the rotational response to apomorphine but provided partial, dose-dependent protection of both ChAT and GAD activity. The rotational response to apomorphine correlated with the percent reduction in both ChAT activity (r = 0.57, P less than 0.0005) and GAD activity (r = 0.49, P less than 0.0005). Rotational behavior may thus provide a means to evaluate the functional integrity of the striatum.