Effects of ethanol on Pavlovian autoshaping in rats.

Approach responses, consummatory behaviors, and directed motor responses maintained by food reward resemble autoshaping CRs and are increased by lower doses of ethanol. This study evaluated the effects of presession i.p. injections of ethanol doses (0.00, 0.25, 0.50, 0.70. or 1.00 g/kg) on the acquisition of lever-press autoshaping CR performance in groups of male Long-Evans hooded rats. Paired groups received 15 daily sessions of Pavlovian autoshaping procedures, wherein the insertion of a retractable lever for 5 s (CS) was followed by the response-independent presentation of food (US). Ethanol facilitated lever-press autoshaping CR acquisition, as revealed by dose-related increases in the number of trials on which CRs were performed. The form of the dose-effect curve was inverted U-shaped with maximal responding induced during sessions 1-5 by the 0.70 g/kg ethanol dose. A similar dose-effect curve was observed during sessions 11-15, revealing that the effects of ethanol on autoshaping CR performance were relatively stable. A pseudoconditioning control group injected presession with 0.50 g/kg ethanol received training wherein the food US was presented randomly with respect to the lever CS. Few lever-presses were performed by the Random 0.50 group, indicating that ethanol's effects on autoshaping CR acquisition and maintenance observed in the Paired 0.50 group were not due to its psychomotor activating effects. A non-injection control group performed more autoshaping CRs than did the control group injected presession with saline, indicating that daily presession i.p. injections per se suppress autoshaping CR performance. Results reveal that low doses of ethanol enhance Pavlovian conditioning of directed motor and consummatory-like responding maintained by food reward. Implications for autoshaping accounts of impulsivity and drug abuse are considered.

Presession noise increases sensitivity to chlordiazepoxide's discriminative stimulus in pigeons.

1. Pigeons were trained to discriminate chlordiazepoxide (CDP) from saline using two-key food reinforced drug discrimination procedures. Discriminative control by CDP was maintained despite extended training with vehicle-like doses of CDP, by using a modified "fading" procedure that provided for a mixture of drug discrimination training sessions preceded by an i.m. injection of either 8.0 mg/kg CDP, or a lower training dose of CDP (4.0, 2.8, 2.0, 1.4, 1.0, 0.7, or 0.5 mg/kg CDP), or saline. The lower training dose was decreased across blocks of sessions. 2. Four lower training doses (1.4, 1.0, 0.7, and 0.5 mg/kg CDP) were retrained, with 10 min of 98 dB of noise administered 75 min prior to each drug discrimination training session. Presession exposure to noise increased percent CDP-appropriate choices for each of the four lower training doses by 15-20% over those obtained previously. 3. It is concluded that brief presession exposure to loud noise increases sensitivity to the discriminative stimulus effects of low training doses of CDP.