Effects of raclopride in the core of the nucleus accumbens on ethanol seeking and consumption: the use of extinction trials to measure seeking.
BACKGROUND
A previous study using a sipper procedure of ethanol self-administration found that blockade of the D2 dopamine (DA) receptors in the nucleus accumbens resulted in a reduction in ethanol-seeking behavior with only slight effects on ethanol drinking. However, because of procedural matters in that study, it was unclear as to the extent of the reduction in seeking behavior that occurred. This study expanded that study to examine in more depth the role of DA transmission in the nucleus accumbens in ethanol-seeking and consummatory behaviors.


METHODS
Male Long-Evans rats were initiated to self-administer 10% ethanol with a sipper-tube procedure. Once initiated, in a once-a-day session, pressing a lever 30 times resulted in a sipper tube containing the ethanol solution being made available for 20 min. By using extinction trials in which no sipper was presented and responses were recorded for 20 min, a measure of ethanol seeking, with no effects of consumption, could be obtained. Bilateral microinjections of 1.0, 3.0, and 10.0 microg of raclopride into the nucleus accumbens were tested on both consummatory and extinction trials.


RESULTS
There were significant decreases in ethanol-seeking responses at both the 3.0- and 10.0-microg doses of raclopride, whereas no effects of those doses on consumption were observed. The effects on extinction responding were the same for the first run of responses as for total responding, without effecting rates of responding.


CONCLUSIONS
These findings replicate and expand the initial study with this model of ethanol self-administration and indicate that DA transmission at the D2 receptor in the nucleus accumbens is important for processing information related to stimulus control and goal-directed behavior. The results also suggest that DA has at most a minor role in controlling ethanol consumption once a drinking bout has begun.
Samson
Herman H
HH
Center for the Neurobehavioral Study of Alcohol, Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1083, USA. hsamson@wfubmc.edu
Chappell
Ann M
AM
D000428:Alcohol Drinking / Q000188:drug therapy* / Q000523:psychology; D000818:Animals; D016739:Behavior, Addictive / Q000188:drug therapy* / Q000523:psychology; D004305:Dose-Response Relationship, Drug; D005108:Extinction, Psychological / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000502:physiology; D020891:Raclopride / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D020318:Rats, Long-Evans; D012646:Self Administration
D020891:Raclopride