Lesion of dopamine mesolimbic neurons blocks behavioral effects induced by the endogenous enkephalins but not by a μ-opioid receptor agonist

Abstract

Lesioning of dopamine neurons by injection of 6-hydroxydopamine into the nucleus accumbens blocked the increased rearing activity measured in the open-field and induced by injection into the ventral tegmental area of: ((R)-3-(N-hydroxylcarboxamido-2-benzyl-propanoyl)-L- alanine), Kelatorphan (complete inhibitor of enkephalin catabolism) or by (Try-D-Ser(OtBu)-Gly-Phe-Leu-Thr(OtBu)): BUBU (selective δ agonist) but not the hypolocomotion evoked by the μ agonist (Tyr-D-Ala-Gly-N(Me)-Phe-Glyol): DAMGO. This suggests the involvement of different neuronal pathways in μ and δ effects.