omega-Conotoxin and ethanol produce similar actions on in vitro calcium channel functions. The present study was designed to determine their possible behavioral interaction. omega-Conotoxin injected ICV at either 0.1 microgram or 0.3 microgram, produced an increase in spontaneous and evoked tremor activity in male Sprague-Dawley rats. The tremor was present at 30 min and continued at least 4 h after injection. At 4 h post ICV injection, animals were given an IP injection of ethanol (3 g/kg body weight). Although no blood alcohol differences were observed between groups, rats injected with omega-conotoxin showed a concentration-dependent increase in sleep times: Saline controls slept for an average of 84.7 +/- 16.7 min, 0.1 and 0.3 microgram conotoxin treated animals slept for 121.3 +/- 16.2 and 211.1 +/- 30.7 min, respectively. These results extend the class of calcium channel blockers capable of producing a behavioral interaction with ethanol.