Amphetamine’s psychomotor and reinforcing effects
Because of the pronounced genotype differences in the psychomotor
effects of AMPH, one could argue that locomotor activity had an
influence on the observed genotype differences after LgA to AMPH
self-administration. However, the lack of genotype differences in AMPH
intake under ShA condition and in the number of incorrect responses
suggests that the increased AMPH intake under LgA condition in
SERT-/- versus SERT+/+ rats did not
result from increased AMPH-induced locomotor activity. Interestingly,
while AMPH self-administration was only increased in
SERT-/- rats under LgA but not ShA conditions, cocaine
self-administration was increased in these animals under both conditions
(Verheij et al., 2018). While we did not conduct a direct comparison
study, this implies that the serotonin influence on AMPH and cocaine
self-administration is different. A potential explanation is that AMPH
and cocaine have a different affinity for SERT (Howell & Kimmel, 2008),
and that serotonin, next to dopamine, contributes to psychostimulant’s
reinforcing effects too.