Ethanol is self-administered into the nucleus accumbens shell, but not the core: evidence of genetic sensitivity.
BACKGROUND
A previous study indicated that selectively bred alcohol-preferring (P) rats self-administered ethanol (EtOH) directly into the posterior ventral tegmental area at lower concentrations than Wistar rats. The present study was undertaken to determine involvement of the nucleus accumbens (Acb) with EtOH reinforcement, and a relationship between genetic selection for high alcohol preference and sensitivity of the Acb to the reinforcing effects of EtOH.


METHODS
Adult P and Wistar rats were assigned to groups that self-infused 0 to 300 mg% EtOH into the Acb shell (AcbSh) or Acb Core (AcbC). Rats were placed into 2-lever (active and inactive) operant chambers and given EtOH for the first 4 sessions (acquisition), artificial cerebrospinal fluid (aCSF) for sessions 5 and 6 (extinction), and EtOH again in session 7 (reinstatement). Responding on the active lever produced a 100-nl injection of the infusate.


RESULTS
Alcohol-preferring rats self-infused 75 to 300 mg% EtOH, whereas Wistar rats reliably self-infused 100 and 300 mg% EtOH into the AcbSh. Both P and Wistar rats reduced responding on the active lever when aCSF was substituted for EtOH, and reinstated responding in session 7 when EtOH was restored. EtOH was not self-infused into the AcbC by P or Wistar rats.


CONCLUSIONS
The present results indicate that the AcbSh, but not AcbC, is a neuroanatomical structure that mediates the reinforcing actions of EtOH. The data also suggest that, compared to Wistar rats, the AcbSh of P rats is more sensitive to the reinforcing effects of EtOH.
Engleman
Eric A
EA
Department of Psychiatry, Institute of Psychiatric Research, Indiana University School of Medicine, Indiana University-Purdue University at Indianapolis, 791 Union Drive, Indianapolis, IN 46202-4887, USA. eenglema@iupui.edu
Ding
Zheng-Ming
ZM
Oster
Scott M
SM
Toalston
Jamie E
JE
Bell
Richard L
RL
Murphy
James M
JM
McBride
William J
WJ
Rodd
Zachary A
ZA
D000428:Alcohol Drinking / Q000235:genetics* / Q000523:psychology; D000818:Animals; D002492:Central Nervous System Depressants / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D008297:Male; D008845:Microinjections; D009714:Nucleus Accumbens / Q000033:anatomy & histology* / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012201:Reward
D002492:Central Nervous System Depressants; D000431:Ethanol