P. Flores et R. Pellon, RATE-DEPENDENCY HYPOTHESIS AND THE RATE-DECREASING EFFECTS OF D-AMPHETAMINE ON SCHEDULE-INDUCED DRINKING, Behavioural pharmacology, 6(1), 1995, pp. 16-23
The high levels of drinking induced by intermittent food-reinforcement
schedules are dose-dependently reduced by acute doses of d-amphetamin
e. The present study evaluated whether the effects of d-amphetamine on
this schedule-induced drinking reflect the reduction of high rates of
responding. Twenty-four rats were divided into six groups (n = 4) acc
ording to the interval and time durations of a multiple fired-time (FT
) fixed-interval (FT) schedule (15 s, 30 s, 60 s, 120 s, 240 s and 480
s). FT components were signalled by a tone and by lever withdrawal. D
oses of 0.25 to 4.0 mg/kg of d-amphetamine were administered i.p. 10 m
in before test sessions. d-amphetamine produced similar dose-dependent
reductions in rate of licking induced by FT and FI schedules. Rate-de
creasing effects on operant lever pressing were also found after admin
istrations of d-amphetamine. The dose-dependent decrements produced by
d-amphetamine were a function of the inter-food interval length in bo
th schedule-induced and operant behaviours. These rate-decreasing effe
cts were rate-dependent, but d-amphetamine interacted differentially w
ith control rates of adjunctive and operant behaviours, causing a grea
ter suppression of the lower rates of adjunctive licking and the highe
r rates of operant lever pressing.