Microdialysis of dopamine in the nucleus accumbens of alcohol-preferring (P) rats during anticipation and operant self-administration of ethanol.
BACKGROUND
The present study was designed to test directly whether a contextual stimulus for access to ethanol would acquire the ability to enhance locomotor activity and dopamine efflux in the nucleus accumbens (NAc) of alcohol-preferring (P) rats. The study also explored the association between elevated locomotor activity and NAc dopamine efflux during operant self-administration of ethanol.


METHODS
Adult female P rats were randomly assigned to operantly self-administer either 15% (v/v) ethanol or 0.0125% (w/v) saccharin. Both groups were trained in a daily 30-min two-lever concurrent operant task (FR-3) to orally self-administer ethanol or saccharin, with water on the alternate lever. A third (control) group was trained to self-administer water on both levers. All groups were also acclimated in the operant chambers to periods of habituation, anticipation, and postadministration.


RESULTS
Compared with controls, the ethanol group, but not the saccharin group, showed significant increases in locomotor activity as well as increased NAc dopamine efflux during the first 10 min of the anticipation period. During the first 10 min of the self-administration period, locomotor activity was significantly increased in both the ethanol and saccharin groups compared with control values. The ethanol group, but not the saccharin group, showed significant increases in NAc dopamine efflux during the 20th and 30th min of the self-administration period and during the first 10 min of the postadministration period.


CONCLUSIONS
The findings suggest that acquisition of signal-induced anticipation of self-administered ethanol is associated with increases in locomotor activity and extracellular levels of dopamine in the NAc of P rats. Such associations may be important to the development and maintenance of ethanol-seeking behaviors. The findings also indicate that operant self-administration of ethanol is associated with increases in extracellular levels of dopamine in the NAc of P rats.
Melendez
Roberto I
RI
Department of Psychology, Program in Psychobiology of Addictions, Purdue School of Science/IUPUI, 402 N. Blackford Street, Indianapolis, Indiana 46202-3275, USA.
Rodd-Henricks
Zachary A
ZA
Engleman
Eric A
EA
Li
Ting-Kai
TK
McBride
William J
WJ
Murphy
James M
JM
D000428:Alcohol Drinking / Q000235:genetics / Q000378:metabolism* / Q000523:psychology; D000818:Animals; D002492:Central Nervous System Depressants / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology*; D015314:Dialysis Solutions / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D017551:Microdialysis / Q000379:methods / Q000706:statistics & numerical data; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D012646:Self Administration / Q000379:methods / Q000523:psychology / Q000706:statistics & numerical data
D002492:Central Nervous System Depressants; D015314:Dialysis Solutions; D000431:Ethanol; D004298:Dopamine