RT Journal Article
SR Electronic
T1 Dramatically Decreased Cocaine Self-Administration in Dopamine But Not Serotonin Transporter Knock-Out Mice
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 1087
OP 1092
DO 10.1523/JNEUROSCI.4037-08.2009
VO 29
IS 4
A1 Morgane Thomsen
A1 F. Scott Hall
A1 George R. Uhl
A1 S. Barak Caine
YR 2009
UL http://www.jneurosci.org/content/29/4/1087.abstract
AB There has been much interest in the relative importance of dopamine and serotonin transporters in the abuse-related-effects of cocaine. We tested the hypotheses that mice lacking the dopamine transporter (DAT−/−), the serotonin transporter (SERT−/−), or both (DAT−/−SERT−/−) exhibit decreased reinforcing effects of cocaine. We also assessed whether observed effects on self-administration are specific to cocaine or if operant behavior maintained by food or a direct dopamine agonist are similarly affected. We used a broad range of experimental conditions that included acquisition without previous training, behavior established with food training and subsequent testing with food, cocaine or a direct dopamine agonist as reinforcers, fixed ratio and progressive ratio schedules of reinforcement, and a reversal procedure. Wild-type mice readily acquired cocaine self-administration and showed dose–response curves characteristic of the schedule of reinforcement that was used. While some DAT−/− mice appeared to acquire cocaine self-administration transiently, almost all DAT−/− mice failed to self-administer cocaine reliably. Food-maintained behaviors were not decreased by the DAT mutation, and IV self-administration of a direct dopamine agonist was robust in the DAT−/− mice. In contrast to those mice, cocaine's reinforcing effects were not diminished in SERT−/− mice under any of the conditions tested, except for impaired initial acquisition of both food- and cocaine-maintained behavior. These findings support the notion that the DAT, but not the SERT, is critical in mediating the reinforcing effects of cocaine.