Alterations in diurnal and nocturnal locomotor activity in rats treated with a monoamine-depleting regimen of methamphetamine or 3,4-methylenedioxymethamphetamine.
BACKGROUND
The long-term neurochemical effects produced by the repeated administration of methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) are well documented; however, the functional consequences have not been clearly defined.


OBJECTIVE
The present study was designed to investigate whether rats treated with a monoamine-depleting regimen of MA or MDMA exhibit disturbances in locomotor activity during the diurnal and nocturnal cycles.


METHODS
Rats were treated with the vehicle or a monoamine-depleting regimen of MA or MDMA (10 mg/kg, IP, every 2 h for four injections on a single day). One week after drug treatment, the rats were placed in residential activity chambers and their locomotor activity was monitored for the next 7-day/night cycles.


RESULTS
MA-treated rats exhibited depletions of striatal dopamine and serotonin content of approximately 70%, whereas MDMA-treated rats showed depletions of striatal serotonin content of approximately 50%. Rats treated with MA demonstrated a significant reduction in diurnal, but not nocturnal, locomotor activity, whereas MDMA-treated rats exhibited significant reductions in both diurnal and nocturnal locomotor activity. Analysis of the difference in activity between the nocturnal and diurnal cycles revealed that MA-treated animals exhibited a significantly greater change in activity as compared to that observed in vehicle- and MDMA-treated rats.


CONCLUSIONS
Although it is unknown whether the adaptations in locomotor activity observed in MA- and MDMA-treated rats are due to the loss of dopamine and/or serotonin, these data suggest that the administration of a monoamine-depleting regimen of MA or MDMA results in alterations in light-cycle-dependent locomotor activity.
Neuroscience Graduate Program, University of Cincinnati, Ohio, USA.
T L
TL
Wallace
G A
GA
Gudelsky
C V
CV
Vorhees
D015104:3,4-Methylenedioxyamphetamine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology; D015259:Dopamine Agents / Q000494:pharmacology*; D008297:Male; D008694:Methamphetamine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D015306:Biogenic Monoamines; D015259:Dopamine Agents; D008694:Methamphetamine; D015104:3,4-Methylenedioxyamphetamine; C051800:3,4-methylenedioxyethamphetamine