EVIDENCE FOR A ROLE OF ENDOGENOUS CANNABINOIDS IN THE MODULATION OF ACUTE AND TONIC PAIN SENSITIVITY

The competitive CB1 receptor antagonist SR141716A was used to test the hypothesis that endogenous cannabinoids modulate tonic pain sensitivi ty. Pretreatment with the antagonist significantly enhanced the respon se to a chemical nociceptive stimulus in the formalin test. Postreatme nt with the antagonist 5 min following the induction of tonic pain pro duced hyperalgesia during the tonic phase only. These findings suggest that endogenous cannabinoids serve naturally to modulate the maintena nce of pain following repeated noxious stimulation. (C) 1998 Elsevier Science B.V. All rights reserved.