Effects of verapamil on the acquisition of ethanol tolerance.

This study investigated the effects of verapamil on the acquisition of tolerance to the ataxic effects of ethanol. Four groups of rats (n = 20/group) were randomly assigned to oral treatment regimes. One group received chronic ethanol treatment (starting at 5 gm/kg/day and increasing by 1 gm/kg at weekly intervals to an eventual dose of 9 gm/kg/day). A second group received the same dose of chronic ethanol together with verapamil (10 mg/kg twice daily). A third group received the same dose of chronic verapamil while the fourth group received chronic placebo treatment. Every fourth day all rats received at least a 2 gm/kg ip test dose of ethanol. Following this, change in motor coordination was measured on an accelerating Rota-Rod treadmill. After six weeks the chronic ethanol group developed tolerance to the test dose of ethanol, while the ethanol and verapamil group did not. Blood ethanol concentrations were not different between the groups. The chronic verapamil and placebo groups developed sensitization to the effects of ethanol but were not different from each other. Chronic treatment with verapamil appeared to delay the acquisition of chronic tolerance to ethanol.