SEROTONERGIC MODULATION OF 3,4-METHYLENEDIOXYMETHAMPHETAMINE (MDMA)-ELICITED REDUCTION OF RESPONSE RATE BUT NOT REWARDING THRESHOLD IN ACCUMBAL SELF-STIMULATION
Hq. Lin et al., SEROTONERGIC MODULATION OF 3,4-METHYLENEDIOXYMETHAMPHETAMINE (MDMA)-ELICITED REDUCTION OF RESPONSE RATE BUT NOT REWARDING THRESHOLD IN ACCUMBAL SELF-STIMULATION, Brain research, 744(2), 1997, pp. 351-357
In a fixed interval 5-s rate-frequency function paradigm with rats, 3,
4-methylenedioxymethamphetamine (MDMA; 0.5, 2 and 4 mg/kg) dose-depend
ently decreased response rate for nucleus accumbens self-stimulation w
hile both D-amphetamine (0.3 and 1 mg/kg) and cocaine (5 and 15 mg/kg)
increased response rates. The highest dose of MDMA caused a cessation
of responding in many of the rats tested, but in those rats that cont
inued to respond a significant reduction in frequency threshold for se
lf-stimulation was seen. Cocaine and amphetamine dose-dependently redu
ced frequency threshold in all rats tested. The non-specific serotonin
antagonist, methysergide (5 mg/kg), reversed the inhibitory effects o
f MDMA on response rates and caused all rats to respond following MDMA
(4 mg/kg). Methysergide did not affect MDMA's threshold-lowering prop
erties and when administered alone methysergide had no effect on self-
stimulation. These results suggest serotonergic involvement in the per
formance but not reinforcement-modulating effect of MDMA in the self-s
timulation paradigm.