Short-access and long-access amphetamine self-administration
After training, rats were divided into 2 groups with an equal number of
AMPH injections during the last 3 training session. One group continued
to self-administer AMPH (0.03 mg/kg/infusion) for 1 hour/day (the short
(ShA) access group: SERT+/+ n= 14,
SERT-/- n=13), and the other group self-administered
the same dose for 6 hours/day (the long (LgA) access group:
SERT+/+ n= 14, SERT-/- n=13) [see
also: (Gipson & Bardo, 2009)]. Protein expression data of these
groups were compared to a new group of animals that was subjected to
surgery, but were not exposed to AMPH (the AMPH-naive group:
SERT+/+ n= 6, SERT-/- n=6; Fig 1b).
The animals were tested daily between 8 am and 6 pm, for 18 consecutive
days [see also: (Verheij et al., 2018)] and the order of testing ShA
and LgA groups was changed every day. Due to a limited number of
self-administration chambers, self-administration was performed in 2
cohorts of SERT+/+ and SERT-/-animals, of which the intake did not differ.