Differential role of D1 and D2 receptors in the perifornical lateral hypothalamus in controlling ethanol drinking and food intake: possible interaction with local orexin neurons.
BACKGROUND
The neurotransmitter dopamine (DA), acting in various mesolimbic brain regions, is well known for its role in promoting motivated behaviors, including ethanol (EtOH) drinking. Indirect evidence, however, suggests that DA in the perifornical lateral hypothalamus (PF/LH) has differential effects on EtOH consumption, depending on whether it acts on the DA 1 (D1) or DA 2 (D2) receptor subtype, and that these effects are mediated in part by local peptide systems, such as orexin/hypocretin (OX) and melanin-concentrating hormone (MCH), known to stimulate the consumption of EtOH.


METHODS
The present study in brain-cannulated Sprague-Dawley rats measured the effects of dopaminergic compounds in the PF/LH on drinking behavior in animals trained to consume 7% EtOH and also on local peptide mRNA expression using digoxigenin-labeled in situ hybridization in EtOH-naïve animals.


RESULTS
Experiments 1 and 2 showed that the D1 agonist SKF81297 (10.8 nmol/side) in the PF/LH significantly increased food intake, while tending to increase EtOH intake, and the D1 antagonist SCH23390 significantly decreased EtOH intake without affecting food intake. In contrast, the D2 agonist quinelorane (6.2 nmol/side) in the PF/LH significantly reduced EtOH consumption, while the D2 antagonist sulpiride increased it. Experiments 3 and 4 revealed differential effects of PF/LH injection of the DA agonists on local OX mRNA, which was increased by the D1 agonist and decreased by the D2 agonist. These DA agonists had no impact on MCH expression.


CONCLUSIONS
These results support a stimulatory role of the PF/LH D1 receptor in promoting the consumption of both EtOH and food, in contrast to a suppressive effect of the D2 receptor on EtOH drinking. They further suggest that these receptors affect consumption, in part, through local OX-expressing neurons. These findings provide new evidence for the function of PF/LH DA receptor subtypes in controlling EtOH and food intake.
Department of Psychology , Princeton University, Princeton, New Jersey; Laboratory of Behavioral Neurobiology , The Rockefeller University, New York, New York.
Yu-Wei
YW
Chen
Irene
I
Morganstern
Jessica R
JR
Barson
Bartley G
BG
Hoebel
Sarah F
SF
Leibowitz
D000428:Alcohol Drinking / Q000378:metabolism*; D000818:Animals; D004435:Eating / Q000502:physiology*; D007028:Hypothalamic Hormones / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism*; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D008543:Melanins / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism; D064446:Orexin Receptors / Q000378:metabolism; D000068797:Orexins; D010907:Pituitary Hormones / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism*
D007028:Hypothalamic Hormones; D047908:Intracellular Signaling Peptides and Proteins; D008543:Melanins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D010907:Pituitary Hormones; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C019463:melanin-concentrating hormone
Dopamine; Ethanol; Lateral Hypothalamus; Melanin-Concentrating Hormone; Orexin