Can chronic pain be suppressed despite purported tolerance to narcotic analgesia?

Abstract

Responsivity to acute nociceptive stimulation and the analgesic response to narcotic drugs was examined in rats exposed to an experimental model of chronic pain, i.e. Mycobacterium butyricum -induced adjuvant arthritis. The major findings are that (i) exposure to chronic pain alone causes hypo-algesia; this hypo-algesia can be attenuated by concurrent narcotics administration; (ii) chronic narcotics administration alone causes hyper-algesia; this hyper-algesia can be attenuated by concurrent exposure to chronic pain; (iii) the tolerance to narcotic analgesia which develops upon chronic narcotics administration in pain-free animals, need not occur in animals concurrently exposed to chronic pain. These findings support a recently proposed hypothesis on pain processing by the central nervous system, and may be suggestive of an effective treatment of chronic pain.