Data and Statistical Analysis
The data and statistical analysis comply with the recommendations on
experimental design and analysis in pharmacology (Curtis et al., 2018).
Previous self-administration studies in cocaine-treated
SERT-/- and SERT+/+ animals have
revealed a significant genotype x self-administration session effect
with an effect-size of about 40% (see a.o. (Verheij et al., 2018)).
Entering this effect size (based on the previously obtained standard
deviation), together with an alpha-value of 0.05 and a power of 0.80,
into G*power (version 3.1), revealed a minimum number of 13 to 14 rats
per genotype. Because of the substantially smaller standard deviation
typically observed in our molecular studies (e.g. Caffino et al., 2020),
the number of animals in the AMPH-naive groups that were not exposed to
self-administration were reduced to 6.