Effects of chronic dietary choline on temporal discrimination of BN and WAG rats

Using rats of the inbred BN and WAG strain, we tested the hypothesis that chronic dietary choline supplementation would especially affect the timing behavior of BN rats because of their lower cholinergic activity and their poor performance in aversively motivated learning and memory tasks. An apparent effect of chronic choline supplementation (2.5 mg choline chloride per ml water) on DRL-8″ responding was not confirmed in a second experiment when the choline concentration was doubled. WAG rats treated chronically with choline showed a poorer temporal discrimination performance on a DRL-16″ schedule than untreated WAG rats. In contrast, choline supplementation never had an effect on the performance of BN rats. The results of the DRL-16″ experiment provide partial support for a hypothesis proposed by Church and Meck that the remembered time of reinforcement is inversely related to the functional activity of brain cholinergic activity: acetylcholine precursor treatment increases memory storage speed, which results in an overestimation of the time elapsed. An alternative explanation, which takes into account the aberrant EEG activities of WAG rats, is also discussed.