"Rodents suppress intake of saccharin when it is paired with a drug of abuse (Goudie, Dickins, & Thornton, 1978; Risinger & Boyce, 2002). By the authors' account, this phenomenon, referred to as reward comparison, is thought to be mediated by anticipation of the rewarding properties of the drug (P. S. Grigson, 1997; P. S. Grigson & C. S. Freet, 2000)," scientists in the United States report.

"Although a great deal has yet to be discovered regarding the neural basis of reward and addiction, it is known that overexpression of Delta FosB is associated with an increase in drug sensitization and incentive. Given this, the authors reasoned that overexpression of Delta FosB should also support greater drug-induced devaluation of a natural reward. To test this hypothesis, NSE-tTA x TetOp-Delta FosB mice (Chen et al., 1999) with normal or overexpressed Delta FosB in the striatum were given access to a saccharin cue and then injected with saline, 10 mg/kg Cocaine, or 20 mg/kg cocaine. Contrary to the original prediction, overexpression of Delta FosB was associated with attenuated cocaine-induced suppression of saccharin intake," wrote C.S. Freet and colleagues, Pennsylvania State University, Medical Department.

The researchers concluded: "It is hypothesized that elevation of Delta FosB not only increases the reward value of drug, but the reward value of the saccharin cue as well."

Freet and colleagues published their study in Behavioral Neuroscience (Overexpression of Delta FosB Is Associated With Attenuated Cocaine-Induced Suppression of Saccharin Intake in Mice. Behavioral Neuroscience, 2009;123(2):397-407).

For additional information, contact C.S. Freet, Pennsylvania State University, College Medical, Dept. of Neural & Behavioral Science, 500 University Dr., H181, Hershey, PA 17033, USA.