Stress induces reinstatement of extinguished cocaine conditioned place preference by a sequential signaling via neuropeptide S, orexin, and endocannabinoid

Abstract

Neurons containing neuropeptide S (NPS) and orexins are activated during stress. Previously, we reported that orexins released during stress, via orexin OX1 receptors (OX1Rs), contribute to the reinstatement of cocaine seeking through endocannabinoid/CB1 receptor (CB1R)‐mediated dopaminergic disinhibition in the ventral tegmental area (VTA). Here, we further demonstrated that NPS released during stress is an up‐stream activator of this orexin‐endocannabinoid cascade in the VTA, leading to the reinstatement of cocaine seeking. Mice were trained to acquire cocaine conditioned place preference (CPP) by context‐pairing cocaine injections followed by the extinction training with context‐pairing saline injections. Interestingly, the extinguished cocaine CPP in mice was significantly reinstated by intracerebroventricular injection (i.c.v.) of NPS (1 nmol) in a manner prevented by intraperitoneal injection (i.p.) of SHA68 (50 mg/kg), an NPS receptor antagonist. This NPS‐induced cocaine reinstatement was prevented by either i.p. or intra‐VTA microinjection (i.vta.) of SB‐334867 (15 mg/kg, i.p. or 15 nmol, i.vta.) and AM 251 (1.1 mg/kg, i.p. or 30 nmol, i.vta.), antagonists of OX1Rs and CB1Rs, respectively. Besides, NPS (1 nmol, i.c.v.) increased the number of c‐Fos‐containing orexin neurons in the lateral hypothalamus (LH) and increased orexin‐A level in the VTA. The latter effect was blocked by SHA68. Furthermore, a 30‐min restraint stress in mice reinstated extinguished cocaine CPP and was prevented by SHA68. These results suggest that NPS is released upon stress and subsequently activates LH orexin neurons to release orexins in the VTA. The released orexins then reinstate extinguished cocaine CPP via an OX1R‐ and endocannabinoid‐CB1R‐mediated signaling in the VTA.

A Role for Neuropeptide S in Alcohol and Cocaine Seeking

“…Indeed, we reported that NPS increased cFos expression in the hypothalamic Hcrt1/Ox-A cells [ 19 , 20 ], and intra-LH injections of NPS (0.5 nmol) markedly increased the cue-induced reinstatement of cocaine seeking [ 20 ], an effect that was abolished by pretreatment with the selective Ox-1 receptor antagonist SB-334867 (10mg/kg, i.p.). In agreement with these data, more recently, Chou and collaborators [ 102 ] demonstrated that i.c.v. infusions of NPS (1 nmol) augmented cFos-containing orexin neurons in the LH and the Ox-A level in the VTA [ 102 ].…”

“…In agreement with these data, more recently, Chou and collaborators [ 102 ] demonstrated that i.c.v. infusions of NPS (1 nmol) augmented cFos-containing orexin neurons in the LH and the Ox-A level in the VTA [ 102 ]. This latter effect was prevented by the NPS receptor antagonist SHA 68 (50 mg/kg, i.p.…”

Role of the Neuropeptide S System in Emotionality, Stress Responsiveness and Addiction-Like Behaviours in Rodents: Relevance to Stress-Related Disorders

“…Such findings suggest that the reinstatement of cocaine-induced CPP by NPS likely involves NPS-cannabinoid-orexin cross-talks in brain areas involved in the behavioural motivation circuit [ 63 ]. This was further confirmed at the molecular level by the observation that NPS increased the activation of orexinergic neurons in the LH as well as enhanced orexin A levels in the ventral tegmental area (VTA) [ 62 ].…”

“…In one study, NPS significantly reduced the expression of morphine-induced CPP but it did not affect the hyper-locomotor effects of morphine [ 61 ], suggesting distinct mechanisms for NPS modulation of the reinforcing and locomotor properties of this drug. In another study, NPS did not affect cocaine-induced CPP expression and extinction [ 62 ]. However, NPS increased the reinstatement of cocaine-induced CPP, which was blocked by the NPSR1 antagonist SHA68, an orexin receptor 1 (ORX1) antagonist (e.g., SB334867) or a cannabinoid receptor 1 (CB1R) antagonist (e.g., AM251).…”

“… CPP Cocaine EXP, EXT [ 62 ] RST Morphine EXP [ 61 ] NPS EXP [ 61 , 65 ] [ 64 ] NPSR1-A i.p. (SHA68) CPP Cocaine RST [ 62 ] RST (stress) X RST (i.c.v. NPS) X NPS i.c.v.…”