Low dose cocaine self-administration by naive rats: effects of body weight and a fixed-time one minute food delivery schedule.

The self-administration rates of four groups of eight rats for low dose cocaine (0.1 mg/kg infusion) under free feeding and 80% body weight conditions, with and without a fixed time 1 min (FT-1) food delivery schedule, were compared with those of saline reinforced animals under the same conditions. Results indicated that (1) overall, self-administration rates were significantly greater for cocaine reinforced animals, (2) significantly higher rates of cocaine self-administration occurred in body weight reduced rats and (3) the operation of FT-1 schedule neither significantly enhanced or inhibited drug intake. In the second experiment, schedule and no schedule conditions were reversed for the sixteen 80% body weight, cocaine reinforced rats. Results showed that reversing schedule and no schedule conditions produced no significant change in drug intake. It was concluded that low dose cocaine self-administration is significantly amplified by body weight reduction.