Neuropeptide S reinstates cocaine-seeking behavior and increases locomotor activity through corticotropin-releasing factor receptor 1 in mice

Abstract

Neuropeptide S (NPS) is a recently discovered neuropeptide that increases arousal and wakefulness while decreasing anxiety-like behavior. Here, we used a self-administration paradigm to demonstrate that intracerebroventricular infusion of NPS reinstates extinguished cocaine-seeking behavior in a dose-dependent manner in mice. The highest dose of NPS (0.45 nM) increased active lever pressing in the absence of cocaine to levels that were equivalent to those observed during self-administration. In addition, we examined the role of the corticotropin-releasing factor receptor 1 (CRF(1)) in this behavior as well as locomotor stimulation and anxiolysis. CRF(1) knock-out mice did not respond to either the locomotor stimulant or cocaine reinstatement effects of NPS, but still responded to its anxiolytic effect. The CRF(1) antagonist antalarmin also blocked the increase in active lever responding in the reinstatement model and the locomotor activating properties of NPS without affecting its anxiolytic actions. Our results suggest that NPS receptors may be an important target for drug abuse research and treatment and that CRF(1) mediates the cocaine-seeking and locomotor stimulant effects of NPS, but not its effects on anxiety-like behavior.

Figure 1.

A, Intracerebroventricular administration of NPS induced cocaine-seeking behavior. SA, Mean of the 3 last days of self-administration; Ext, mean of the 2 last days of extinction. The highest dose of NPS significantly increased lever pressing in the absence of cocaine (N = 8; p = 0.002). B, The highest dose of NPS did not increase lever pressing in drug-naive mice (N = 6). The data are represented as means ± SEM. Statistical significance was calculated by ANOVA and Bonferroni's corrections were made for the subsequent pairwise comparisons such that significance was set at p < 0.0125. *Significant versus saline.

Figure 2.

NPS effects on cocaine reinstatement are mediated by CRF₁. SA, Mean of the 3 last days of self-administration; Ext, mean of the 2 last days of extinction; Sal, saline injection. A, B, Lever pressing in C57BL/6J mice pretreated with vehicle or antalarmin followed by saline or NPS (N = 9) (A) and in WT and CRF₁ KO mice treated with saline or NPS (N = 12) (B). The data are represented as means ± SEM. Statistical significance was calculated by ANOVA and Bonferroni's corrections were made for the subsequent pairwise comparisons such that significance was set at p < 0.0125. *Significant versus vehicle/saline.

Figure 3.

NPS increases locomotor activity through a CRF₁-dependent mechanism. A, B, Locomotor activity in response to NPS after pretreatment with vehicle or antalarmin in C57BL/6J mice (N = 39) (A) and in CRF₁ WT and KO mice (N = 27) (B). The data are represented as means ± SEM. Statistical significance was calculated by ANOVA and Bonferroni's corrections were made for the subsequent pairwise comparisons such that significance was set at p < 0.016. *Significant versus vehicle/saline.

Figure 4.

NPS decreases anxiety-like behavior through a CRF₁-independent mechanism. A, B, Light/dark transfer behaviors in response to NPS after pretreatment with vehicle or antalarmin in C57BL/6J mice (N = 16) (A) and in CRF₁ WT and KO mice (N = 20) (B). The left panels show the time (in seconds) spent in the light compartment, and the right panels show the number of transitions the mice made between the dark and light compartments of the apparatus. C, Marbles buried after NPS in CRF₁ WT and KO mice. The data are represented as means ± SEM. Statistical significance was calculated by two-way between-subjects ANOVA. *Indicates overall significant effect of treatment (saline vs NPS).