Influence of pertussis toxin on the calcitonin‐opioid interaction in isolated tissues

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Abstract
1 In order to clarify one of the mechanisms involved in the analgesic effect of calcitonin, we have tested the in vitro modifications induced by calcitonin on the effect of opioids. 2 The inhibition of the contractions induced by opioids or clonidine, in guinea-pig ileum or in mouse vas deferens, were significantly reduced in tissues incubated with pertussis toxin (PTX). When tissues were incubated with PTX and calcitonin, the inhibitory effect was restored. 3 These results suggest that calcitonin is able to potentiate a non-PTX-sensitive mechanism of transduction and support the possibility of involvement of similar G-proteins in the effects of opioid and α2-adrenoceptor agonists.