Ka. Miczek et M. Naney, PSYCHOMOTOR STIMULANT EFFECTS OF D-AMPHETAMINE, MDMA AND PCP - AGGRESSIVE AND SCHEDULE-CONTROLLED BEHAVIOR IN MICE, Psychopharmacology, 115(3), 1994, pp. 358-365
The objective of the present experiments was to characterize psychomot
or stimulant effects of d-amphetamine, methylenedioxymethamphetamine (
MDMA) and phencyclidine (PCP) on conditioned performance and on aggres
sive behavior in mice. In a novel protocol with alternating periods of
schedule-controlled responding and aggressive behavior toward an intr
uder it was possible to assess a range of species-specific agonistic a
cts, postures, and motor activities as well as response rates and patt
erns engendered by a multiple Fixed Interval (FI) and Fixed Ratio (FR)
schedule within the same animal. Initially, it was confirmed that d-a
mphetamine and, less reliably, MDMA and PCP, increased FI, but not FR
responding in mice. In the next experiment, mice confronted an intrude
r at the midpoint of the 1-h daily session; following the display of a
ggressive behavior, the rate of FI responding showed an amphetamine-li
ke increase, whereas only a transient change occurred after non-aggres
sive encounters. Thirdly, using this new protocol, PCP, d-amphetamine
and MDMA altered FI and FR responding in a way that was closely simila
r to the first experiment. Low PCP and d-amphetamine doses increased a
ggressive behavior erratically in certain individuals, but not reliabl
y for the group. MDMA dose-dependently decreased aggressive behavior,
and all drugs disrupted aggressive behavior at higher doses. The chara
cteristic increases in walking and decreases in rearing after higher d
oses of PCP and d-amphetamine were greatly attenuated when the intrude
r was present. The rate-increasing effects of d-amphetamine, MDMA and
PCP occurred in the early portion of the fixed interval when the contr
ol rate is typically low; by contrast, low attack rates during the lat
er portion of the confrontation with the intruder remained unaffected.
The dose-dependent quantitatively and qualitatively differentiated pr
ofile of effects on schedule-controlled responding, motor activity and
aggressive behavior suggest that the common properties of d-amphetami
ne, MDMA and PCP pertain mostly to the disruption of organized behavio
r patterns and activation of repetitive motor routines at high doses,
but point to different mechanisms for modulating aggressive behavior a
nd conditioned performance at lower doses.-