Barbiturate dependence and drug preference.

Rats exposed to a daily 3-hr session of intermittent food delivery ingested physical-dependent levels of a 1 mg/ml sodium phenobarbital solution. This chronic, voluntary, high level of session phenobarbital intake had no effect on 21-hr home cage barbiturate preference. Substitution of water for phenobarbital during the session after 7.5 weeks precipitated various spontaneous withdrawal signs in some of the animals by the 24th hr of drug withdrawal but no change was found in home-cage barbiturate preference at any time. Physical dependence alone does not seem to play a crucial role in the maintenance of drug intake behavior.