Expression of Fos-related antigens in the nucleus accumbens during opiate withdrawal and their attenuation by a D2 dopamine receptor agonist

Previous studies from this laboratory indicated that D2 dopamine (DA) recep tors within the nucleus accumbens (NAc) are important for regulating somati c signs of opiate withdrawal. The present study measured the expression of Fos-related antigens (FRAs) within the NAc during opiate withdrawal to dete rmine whether decreases in somatic withdrawal signs produced by a D2 recept or agonist are accompanied by related changes in accumbens neuronal activit y. In an initial experiment, quantitative analyses of FRA immunoreactivity revealed increases in the number of FRA-positive cells throughout the NAc o f opiate dependent animals undergoing naltrexone-precipitated withdrawal re lative to dependent or non-dependent animals that did not experience withdr awal. A second experiment showed that somatic signs and FRA expression with in the NAc could each be attenuated when the D2 agonist propylnorapomorphin e (NPA; 0.1 or 0.3 mg/kg, i.p.) was administered prior to naltrexone-precip itated withdrawal. These findings suggest that D2 regulation or neuronal ac tivity within the NAc may be important for the expression of opiate withdra wal symptoms. (C) 2000 American College of Neuropsychopharmacology. Published by Elsevier Science Inc. All rights reserved.