Evidence that ethanol-induced impairment of roto-rod performance is not mediated by opioid mechanisms.

1. The performance of mice, trained to remain on a roto-rod, was significantly impaired by both morphine and ethanol. The behavioral impairment was dose dependent. 2. Naloxone (10, 30 and 100 mg/kg) was found to antagonize only the morphine-induced impairment of roto-rod performance. 3. Animals made tolerant to morphine did not perform better than non-tolerant animals when challenged with ethanol, but did perform better when challenged with morphine. As such, no cross tolerance developed between ethanol and morphine in this model. 4. These results suggest that the ethanol-induced impairment of roto-rod performance is not mediated via opioid mechanisms.