Haloperidol affects stimulus-dependent strategies and not reward-dependent strategies.

In order to investigate effects of haloperidol on response strategies, rats were confronted with an unsolvable discrimination problem after being injected with haloperidol (0.1 mg/kg, IP) or its solvent. The results showed that haloperidol-treated rats displayed systematic behaviour to a lesser degree than the control rats.

Chronic dietary choline enrichment affects DRL responding of old, but not of adult CPBB rats.

Using adult (11-month-old) and aged (22-month-old) inbred female CPBB rats, we tested the hypothesis that chronic dietary choline supplementation affects timing behavior. The rats had received choline chloride in their tap water for about 9 months before they acquired responding on a differential reinforcement of low-rate schedule with a critical delay of 8 s (DRL-8"). One retention session and two extinction sessions were given 4 weeks after the end of acquisition.

Problem-solving behaviour in apomorphine-susceptible and unsusceptible rats.

Pharmacogenetically selected apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats were trained in a discrimination learning paradigm. After the initial discrimination task was solved, reinforcement contingencies were reversed. No differences between APO-SUS and APO-UNSUS animals were found in the rate of learning.

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.

Genetic correlations in validating emotionality.

Sixty-six rats of seven inbred strains were observed in an open field (OF) and in a light-dark preference box (LDB). Each set of apparatus provides measures of locomotor activity and of the time spent in the "most protected" area (the corners in the OF, the dark compartment in the LDB). These measures are proposed to be indices of emotionality.