Interaction of CRH and energy balance in the modulation of brain stimulation reward.

The rewarding effect produced by electrical stimulation of some lateral hypothalamic sites is modulated by chronic food restriction and weight loss. The sensitivity of the rewarding effect to restriction predicts the modulation of brain stimulation reward (BSR) by the adiposity hormone, leptin. The present study examined the effect of corticotropin-releasing hormone (CRH) on the rewarding effect of stimulating restriction-sensitive and restriction-insensitive sites. Chronic food restriction reduced frequency thresholds for BSR in half of the subjects but had no effect in the others. CRH increased thresholds only in subjects in which the rewarding effect was insensitive to restriction. In contrast, frequency thresholds remained stable in nearly all rats with restriction-sensitive stimulation sites. These findings provide further evidence that sensitivity to food restriction is an important factor in determining the influence of hormones and neuropeptides on brain reward circuitry.