Reduced sensitivity to reward in CB1 knockout mice

Authors: Sanchis-Segura, Carles¹; Cline, Brandon¹; Marsicano, Giovanni²; Lutz, Beat²; Spanagel, Rainer³

Source: Psychopharmacology, Volume 176, Number 2, November 2004 , pp. 223-232(10)

Publisher: Springer

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Abstract:

Previous studies have demonstrated that the activation and blockade of the cannabinoid type 1 receptor (CB1) leads to an enhancement and decrease of the consumption of food and other orally ingested reinforcers, respectively.

To gain further knowledge about the role of CB1 in sucrose/saccharin reinforcing efficacy and intake, we tested CB1 knockout (CB1-KO) and littermate wild-type (WT) control mice in several self-administration experimental protocols.

Operant (fixed or progressive ratio schedule) and non-operant conditioning procedures were used. In addition, a choice analysis based on the “matching law” as well as a microstructural analysis of the intra-session pattern of self-administration was performed.

CB1-KO mice consume less sucrose under operant conditions or when using a two-bottle free choice procedure. Moreover, as revealed by additional behavioural analysis, CB1-KO mice exhibit a decreased sensitivity to the rewarding properties of sucrose. In agreement with this finding, the differences between WT and CB1-KO mice faded away when the palatability of sucrose was devaluated by adding quinine, but not when a non-caloric sweetener, saccharin, was available.

These results demonstrate a modulatory role of CB1 in the determination of the rewarding properties of sucrose and probably, as suggested by previous studies, other reinforcers.

Keywords: Cannabinoid receptor 1; Sucrose; Reinforcing efficacy; Reward; Matching law

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s00213-004-1877-8

Affiliations: 1: Department of Psychopharmacology, Central Institute for Mental Health, CIMH, University of Heidelberg, 68159, Mannheim, Germany, 2: Molecular Genetics of Behaviour, Max Planck Institute of Psychiatry, Munich, Germany, 3: Department of Psychopharmacology, Central Institute for Mental Health, CIMH, University of Heidelberg, 68159, Mannheim, Germany, Email: spanagel@zi-mannheim.de

Publication date: 2004-11-01

Reduced sensitivity to reward in CB1 knockout mice

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