Effect of salmon-calcitonin on the analgesic effect of selective mu, deltaand kappa opioid agonists in mice

The analgesic effect of three different opioid agonists, DAMGO ([D-Ala(2),M -Me-Phe(4),Gly(5)-ol]enkephalin), U-50,488H (trans-3,4-dichloro-N-methyl-N- [2-(1-pyrrolidynyl)cyclohexyl] benzene-aceramide methane sulphonate), and [ D,Pen(2)-D,Pen(5)]-enkephalin, which act upon mu, delta and kappa opioid re ceptors, respectively, was compared in the presence and absence of salmon-c alcitonin (s-CT). The analgesic test used was the writhing test in mice. Th e analgesic effect of the opioids was significantly enhanced by pretreatmen t of the animals with s-CT intraperitoneally (i.p.) administered. This effe ct was more evident for the delta and kappa-agonists. The present result su ggests that the joint administration of s-CT and opioids may be a useful an d interesting alternative in the treatment of painful diseases resistant to other treatments. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.