beta-funaltrexamine and saclofen

Food intake is significantly increased by administration of mu-selective opioid agonists into the nucleus accumbens, particularly its shell region. Pretreatment with either opioid (mu, delta(1), delta(2) or kappa(1)) or dopaminergic (D(1)) receptor antagonists in the nucleus accumbens shell reduce mu opioid agonist-induced feeding. Selective GABA(A) (muscimol) and GABA(B) (baclofen) agonists administered into the nucleus accumbens shell each stimulate feeding which is respectively and selectively blocked by GABA(A) (bicuculline) and GABA(B) (saclofen) antagonists. The present study investigated whether feeding elicited by the mu-selective opioid agonist, [D-Ala(2),NMe(4),Gly-ol(5)]-enkephalin in the nucleus accumbens shell was decreased by intra-accumbens pretreatment with an equimolar dose range of either GABA(A) or GABA(B) antagonists, and further, whether general opioid or selective GABA antagonists decreased feeding elicited by GABA(A) or GABA(B) agonists in the nucleus accumbens shell. Feeding elicited by the mu-selective opioid agonist was dose-dependently increased following intra-accumbens pretreatment with GABA(A) (bicuculline) antagonism; this enhancement was significantly blocked by pretreatment with general or mu-selective opioid antagonists. In contrast, mu opioid agonist-induced feeding elicited from the nucleus accumbens shell was dose-dependently decreased by GABA(B) (saclofen) antagonism. Neither bicuculline nor saclofen in the nucleus accumbens shell altered baseline food intake. Whereas muscimol-induced feeding elicited from the nucleus accumbens shell was reduced by bicuculline and naltrexone, but not saclofen pretreatment, baclofen-induced feeding elicited from the nucleus accumbens shell was reduced by saclofen, but not by bicuculline or naltrexone. These data indicate that GABA(A) and GABA(B) receptor subtype antagonists differentially affect feeding elicited by mu opioid receptor agonists within the nucleus accumbens shell in rats.

Topics: Animals; Baclofen; Bicuculline; Eating; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; GABA Agonists; GABA Antagonists; GABA-A Receptor Antagonists; GABA-B Receptor Antagonists; gamma-Aminobutyric Acid; Male; Naltrexone; Narcotic Antagonists; Narcotics; Neurons; Nucleus Accumbens; Rats; Rats, Sprague-Dawley; Receptors, GABA; Receptors, GABA-A; Receptors, GABA-B; Receptors, Opioid