Effects of naloxone and chlordiazepoxide on lateral hypothalamic self-stimulation in rats.

Lateral hypothalamic self-stimulation behavior of rats in an operant chamber was investigated under the treatments of the first injection of naloxone (5 mg/kg) or saline followed by the second injection of chlordiazepoxide (4 mg/kg) or saline. Both inhibitory effect of naloxone and facilitatory effect of chlordiazepoxide on self-stimulation response were statistically significant, but the interaction between the two effects was not obtained. The results indicate that the facilitatory effect of chlordiazepoxide upon self-stimulation is independent of endogenous opioid system. Further, the obtained effect of naloxone was discussed in terms of interaction of the drug with aversive, rather than rewarding, component of self-stimulation.