Effect of the noncompetitive NMDA antagonists MK-801 and ketamine on the spastic Han-Wistar mutant: a rat model of excitotoxicity.

The neuroprotective effects of the NMDA antagonists MK-801 and ketamine were analyzed in a mutant strain of Han-Wistar rats which develop neurodegeneration in the hippocampus and cerebellum. Previous experiments have shown that the progressive neuronal degeneration observed in this mutant may be the result of a dysfunctional glutamatergic system. For MK-801 studies, mutants were injected in a chronic paradigm with (+)MK-801 or its weaker acting isomer (-)MK-801 at a dose of 1 mg/kg. Ketamine studies consisted of both acute (50 mg/kg once) and chronic (10 mg/kg multiple times) injection paradigms. MK-801-treated mutants exhibited longer life spans (8-23%) compared to saline-injected mutants. Ketamine-injected mutants in both paradigms also lived slightly longer (6-9%) than the saline mutants. Motor skill deterioration was monitored in an open-field test, and after 50 days of age the MK-801 and ketamine mutants displayed over 20% greater motor skill activity than the saline mutants. In the cerebellum, mutants treated with ketamine and both forms of MK-801 had 10-20% more Purkinje cells surviving at 55 days than the saline mutants. Further, the density of CA3c pyramidal hippocampal neurons in ketamine and MK-801-treated mutants as compared to saline mutants appeared to be greater upon qualitative analysis. This study shows that these mutants derive some protective effects from the NMDA antagonists MK-801 and ketamine, confirming glutamate-induced excitotoxicity as a possible cause of neuronal degeneration in this mutant strain of rat. Copyright 2001 S. Karger AG, Basel