HYPERACTIVITY, HYPERREACTIVITY, AND SENSORIMOTOR DEFICITS INDUCED BY LOW-DOSES OF THE N-METHYL-D-ASPARTATE NONCOMPETITIVE CHANNEL BLOCKER-MK801

Three doses of MK801 (0.05 mg/kg, 0.3 mg/kg and 1.0 mg/kg) were given systemically to adult male rats, which were then tested on a battery o f previously learned, reactive and spontaneous behaviors. Hyperactivit y, hyper-reactivity, reductions in rearing behavior and deficits in to ngue extension were found at the 0.05 mg/kg dose. Similar, but more se vere results were found at the 0.3 mg/kg dose, with the addition of di fficulties in climbing, balancing on a beam, and abnormalities in orie nting to tactile stimuli. A number of tasks could not be performed at the 1.0 mg/kg dose including tongue extension, orienting, balancing on a beam, and climbing. Additionally, abnormal postures, gaits, and swi mming behaviors were observed at this dose. These results characterize the behavioral effects of MK801 as a syndrome of hyperactivity, hyper -reactivity, and sensorimotor deficits. Evidence of this syndrome was present at all three doses, including the 0.05 mg/kg dose, which previ ously has been claimed to induce deficits similar to hippocampal lesio ns. Learning literature employing MK801 is discussed in the context of the behavioral deficits found in this study.