Ukai M, Mori E, Kameyama T
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Japan.
Pharmacol Biochem Behav. 1995 Aug;51(4):705-8. doi: 10.1016/0091-3057(95)00010-t.
The present study was designed to investigate the effects of centrally administered neuropeptides on the discriminative stimulus properties of cocaine in the rat. Rats were trained to discriminate 10.0 mg/kg of cocaine from vehicle in a shock avoidance paradigm. The mu-selective opioid agonist [D-Ala2,NMePhe4,Gly-ol]enkephalin (DAMGO) (0.03-0.3 microgram, ICV) or the kappa-selective opioid agonist dynorphin A-(1-13) (1.0-10.0 micrograms, ICV) did not generalize to cocaine cue, although the delta-selective opioid agonist [D-Pen2,L-Pen5]enkephalin (DPLPE) (10.0 micrograms, ICV) reportedly generalizes to it through the mediation of delta-opioid receptors. Thyrotropin-releasing hormone (10.0-56.0 micrograms, ICV), somatostatin (0.3-3.0 micrograms, ICV), substance P (3.0-17.5 micrograms, ICV), or neurotensin (3.0-17.5 micrograms, ICV) did not produce any stimulus effects in common with cocaine. It appears that neuropeptides other than the delta-selective opioid do not play a major role in the discriminative stimulus properties of cocaine.
