Effects of intraaccumbens injections of dopamine agonists and antagonists on sucrose and sucrose-ethanol reinforced responding.
The present experiment tested the effects of intraaccumbens injections of dopamine (DA) agonists and antagonists on operant responding reinforced by sucrose and sucrose/ethanol solutions. The mixed DA agonist d-amphetamine (20.0 micrograms/microliters) significantly reduced responding reinforced by a low concentration sucrose solution (2% w/v) by 48% and 38% compared to no injection and sham control values, respectively. The addition of ethanol (10%) to a low concentration sucrose solution (3%) presented as the reinforcer changed the response pattern from a continuous moderate response rate, over a 30 min session, to an initial high response rate that terminated after approximately 10 min. With sucrose/ethanol reinforcement, d-amphetamine slowed the initial high response rate but extended responding throughout the 30 min sessions. However, no significant changes were observed in number of responses per session. When 75% sucrose (w/v) was presented as the reinforcer, d-amphetamine did not change the total number of responses/session, but response patterns were again altered from high initial rates with early offset to slow steady rates that continued for the duration of sessions. The D2 DA antagonist raclopride (0.1-5.0 micrograms/microliters) resulted in a dose-dependent decrease in responding reinforced by 75% sucrose. The baseline patterns, response totals, and effects of the DA antagonists resemble our previously reported findings with 10% ethanol (v/v) reinforcement. These data support the conclusion that mesolimbic DA activity may be a common mechanism in ethanol reinforced behavior and behavior reinforced by other substances, but suggest that the nature of behavioral change may depend upon the reinforcer.
Hodge
C W
CW
Department of Physiology and Pharmacology, Wake Forest University, Bowman Gray School of Medicine, Winston-Salem, NC 27157.
Samson
H H
HH
Tolliver
G A
GA
Haraguchi
M
M
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology; D015259:Dopamine Agents / Q000008:administration & dosage / Q000494:pharmacology*; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D004873:Ergolines / Q000008:administration & dosage / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D008297:Male; D008845:Microinjections; D009714:Nucleus Accumbens / Q000033:anatomy & histology / Q000502:physiology*; D019257:Quinpirole; D020891:Raclopride; D051381:Rats; D012054:Reinforcement, Psychology; D012457:Salicylamides / Q000008:administration & dosage / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology*
D015259:Dopamine Agents; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004873:Ergolines; D012457:Salicylamides; D019257:Quinpirole; D000431:Ethanol; D020891:Raclopride; D013395:Sucrose; D003913:Dextroamphetamine