Corticotropin-releasing factor as well as opioid and dopamine are involved in tail-pinch-induced food intake of rats.

Several kinds of stress such as psychological stress, restraint, and foot shock inhibit feeding behavior through corticotropin-releasing factor (CRF). In contrast, a mild tail pinch increases food intake in rats. Although dopamine and opioid are thought to be involved in tail-pinch-induced food intake, it is unknown whether CRF participates in this phenomenon. Therefore, we attempted to clarify this issue using rats. A 30-s tail pinch increased food intake in 30 min after the tail pinch, and this increase was blocked by intraperitoneal injection of CRF receptor type 1 selective antagonist. CRF increased food intake in 30 min after intracerebroventricular injection at a dose of 2 or 10 ng, and this increase was also blocked by CRF receptor type 1 antagonist. Tail-pinch- or CRF-induced food intake was blocked by naloxone, pimozide, and spiperone. These results suggest that CRF, through CRF receptor type 1 as well as opioid and dopaminergic systems, are involved in the mechanism of tail-pinch-induced food intake. The results also suggest that brain CRF has dual effects on food intake, hyperphagia and anorexia, in a stress-dependent manner.