Orexin-1 receptor antagonism does not reduce the rewarding potency of cocaine in Swiss-Webster mice

The orexin family of hypothalamic neuropeptides has been implicated in reinforcement mechanisms relevant to both food and drug reward. Previous behavioral studies with antagonists at the orexin A-selective receptor, OX1, have demonstrated its involvement in behavioral sensitization, conditioned place-preference, and self-administration of drugs of abuse. Adult male Swiss-Webster mice were implanted with stimulating electrodes to the lateral hypothalamus and trained to perform intracranial self-stimulation (ICSS). The effects of the OX1-selective antagonist SB 334867 on brain stimulation-reward (BSR) and cocaine potentiation of BSR were measured. SB 334867 (10-30 mg/kg, i.p.) alone had no effect on ICSS performance or BSR threshold. Cocaine (1.0-30 mg/kg i.p.) dose-dependently potentiated BSR, measured as lowering of BSR threshold. This effect was not blocked by 30 mg/kg SB 334867 at any cocaine dose tested. In agreement with previous reports, SB 334867 resulted in a reduction of body weight 24 h after acute administration. Based on these data, it is concluded that orexins acting at OX1 do not contribute to BSR; and are not involved in the reward-potentiating actions of cocaine on BSR. The data are discussed in the context of prior findings of SB 334867 effects on drug-seeking and drug-consuming behaviors. (C) 2011 Elsevier B.V. All rights reserved.