Intraventricular self-administration of acetaldehyde, but not ethanol, in naive laboratory rats.

For 11 consecutive days, naive rats were maintained in operant chambers where they were given the opportunity to self-administer acetaldehyde (1,2, or 5% v/v), ethanol (2 or 10% v/v), or pH control solutions directly into the cerebral ventricles. Only the animals that had access to the 2 and 5% acetaldehyde solutions showed rates of lever pressing significantly higher than controls. It is suggested that acetaldehyde rather than ethanol itself may mediate the positive reinforcing effects of ethanol in the brain.