title: Morphine and self-stimulation: evidence for action on a common neural substrate.
abstract: Recent studies have demonstrated that the self-stimulation phenomenon may provide a useful technique for investigating the rewarding properties of potentially addictive drugs such as morphine. The present study attempted to examine the nature of morphine's effects on self-stimulation by observing changes in rate-intensity functions following morphine administration. The results indicate that morphine markedly enhanced bar pressing for low intensity stimulation when the intensities were presented in an ascending sequence but morphine produced only slight changes in self-stimulation rates when a descending series was used. The failure of morphine to facilitate responding in the descending series suggests that adaptation of the self-stimulation system can block morphine's effects on this system. These findings appear to support the hypothesis that morphine affects the excitability of the neural system which mediates self-stimulation.
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology; D004558:Electric Stimulation; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D012653:Self Stimulation / Q000187:drug effects*
chemical_list: D009020:Morphine