ABSTRACT
1. The modifications in rat behaviour caused by chronic manipulations of dietary choline were studied in two schedules of operant conditioning. Adult rats were maintained on choline-deficient, low-choline and high-choline enriched diets. 2. In the "periodic conditioning" test, the schedule of reinforcement was changed from a fixed ratio to a fixed interval schedule. In the "reversal" test the contingency for food delivery was switched four times from one lever to the other in a two lever Skinner box. 3. In the "periodic conditioning" test, control and treated groups showed the same reduction of responses/reinforcement from the beginning to the end of trial. The time-course reduction of responses/reinforcement became significant in the high-choline (331 mg/kg/day) and deficient-choline groups earlier than in the low-choline (75 mg/kg/day) enriched and control groups. 4. In the "reversal" test, the low-choline (110 mg/kg/day) enriched diet improved the reinforced responses in the IV reversal; the high-choline (330 mg/kg/day) diet gave a significant impairment of the reinforced responses in the III and IV reversals. The deficient-choline diet caused a reduced number of the total responses and a worsening of the reinforced responses in the II, III and IV reversals.
