Role of amygdala dopamine D1 and D2 receptors in the acquisition and expression of fructose-conditioned flavor preferences in rats.
Systemic administration of dopamine D1-like (SCH23390) and, to a lesser degree D2-like (raclopride), receptor antagonists significantly reduce the acquisition and expression of fructose-conditioned flavor preferences (CFP) in rats. Given the role of dopamine in the amygdala (AMY) in the processing and learning of food reward, the present study examined whether dopamine D1-like or D2-like antagonists in this site altered acquisition and/or expression of a fructose-CFP. In Experiment 1, food-restricted rats with bilateral AMY cannulae were trained to drink a fructose (8%)+saccharin (0.2%) solution mixed with one flavor (e.g., grape, CS+/Fs) and a less-preferred 0.2% saccharin solution mixed with another flavor (e.g., cherry, CS-/s) during one-bottle (16 ml) sessions. Two-bottle tests with the two flavors mixed in saccharin solutions (CS+/s, CS-/s) occurred 10 min following total bilateral AMY doses of 0, 12, 24 and 48 nmol of SCH23390 or raclopride. Preference for CS+/s over CS-/s was significantly reduced relative to vehicle baseline by the 48 nmol doses of SCH23390 and raclopride (from 77% to 66% and 68%), but not lower doses. In Experiment 2, rats received bilateral AMY injections (12 nmol) of SCH23390 (D1 group) or raclopride (D2 group) 10 min prior to one-bottle training sessions with CS+/Fs and CS-/s. Yoked Control rats received vehicle and were limited to the CS intakes of the D1 and D2 groups; untreated controls were not injected or limited to drug group intakes during training. Subsequent two-bottle tests revealed initial preferences of CS+/s over CS-/s in all groups that remained stable in untreated and Yoked Controls, but were lost over the 6 tests sessions in the D1 group, but not in the D2 group. These data indicate that dopamine D1-like and D2-like antagonists significantly attenuated the expression of the previously acquired fructose-CFP, and did not block acquisition of the fructose-CFP. D1-like antagonism during training hastened extinction of the fructose-CFP. The results are similar to those produced by dopamine D1-like and D2-like antagonist injections into the nucleus accumbens shell which suggests that flavor conditioning involves a regionally distributed brain network.
Bernal
Sonia
S
Neuropsychology Doctoral Subprogram, Graduate Center, City University of New York, New York, NY 11367, United States.
Miner
Patricia
P
Abayev
Yana
Y
Kandova
Ester
E
Gerges
Meri
M
Touzani
Khalid
K
Sclafani
Anthony
A
Bodnar
Richard J
RJ
D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001552:Benzazepines / Q000008:administration & dosage / Q000494:pharmacology; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D018492:Dopamine Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D004327:Drinking Behavior / Q000187:drug effects / Q000502:physiology; D005632:Fructose / Q000008:administration & dosage; D008297:Male; D010812:Physical Stimulation; D020891:Raclopride / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012439:Saccharin / Q000008:administration & dosage; D055697:Taste Perception / Q000187:drug effects / Q000502:physiology*
D001552:Benzazepines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C534628:SCH 23390; D005632:Fructose; D020891:Raclopride; D012439:Saccharin