title: Environmentally induced analgesia: an age-related decline in an endogenous opioid system.
abstract: The purpose of the present study was to examine in rats the relationship between the age-related decline in an opioid receptor system and the function of the endogenous opioid pain-inhibitory system activated by front-paw shock. Results revealed that the analgesia displayed following front-paw shock declined between 5- to 7-month-old, 15- to 17-month-old, and 22- to 24-month-old age groups. The administration of naloxone significantly attenuated the shock-induced analgesia. Thus, the endogenous opioid pain modulatory system activated by front-paw shock (the nucleus raphe alatus and a descending pathway lying within the dorsolateral funiculus of the spinal cord) declines in function with increasing age. This research also confirms that there is a parallel between the age-related decline in the neurochemical indexes of the opioid receptor system and the function of these receptors in producing analgesia in response to aversive stimulation.
authors.forename: R J
authors.initials: RJ
authors.lastname: Hamm
authors.forename: J S
authors.initials: JS
authors.lastname: Knisely
mesh_terms: D000375:Aging; D000698:Analgesia; D000818:Animals; D004597:Electroshock; D007274:Injections, Intraperitoneal; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects* / Q000503:physiopathology; D013997:Time Factors
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone