Proefschrift_Holstein

Chapter 3

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Error rate (%): Switch cost (switch - repeat) placebo bromo- criptine bromo- criptine & sulpiride

sulpiride

Drug

to Bond and Lader (1974) see supplementary results) were available for 46 subjects. For each session we calculated the drug-induced change in prolactin and mood ratings (after - before drug intake) and compared this with the placebo-induced change [difference score = (drug session (Time2 –Time1)) – (placebo session (Time2 – Time1))] (supplementary results: table S3.1 + mood measures). Pearson correlations were calculated, in the 10R homozygotes, between trait anxiety (STAI), trait impulsivity (BIS-11), depression (BDI), listening span scores, bromocriptine-induced mood changes, bromocriptine-induced prolactin changes and bromocriptine-induced changes in task switching. Results Genetic variation predicts the effect of bromocriptine on task switching All 48 subjects performed the pre-cued task-switching paradigm after receiving a placebo or the dopamine receptor agonist bromocriptine (1.25 mg). Under placebo, there was no difference in terms of task switching between the DAT1 genotype groups [error rates; Switching x DAT1 : F(1,46) < 1]. However, consistent with our Figure 3.3 Sulpiride abolished the effect of bromocriptine Shown is the switch cost (switch – repeat) in error rate (percent) for the 10R homozygotes (n = 14) who received pre-treatment with sulpiride, as well as bromocriptine and sulpiride alone. In this smaller group, bromocriptine also reduced the switch cost relative to placebo. However, when the same subjects received sulpiride pre-treatment, bromocriptine no longer facilitated task switching. Error bars represent the standard error of the difference between switch and repeat trials.

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