Effect of salmon-calcitonin on in vitro opioid withdrawal

The effect on the in vitro withdrawal sign induced by naloxone in morphine-dependent guinea pig ileum has been analyzed. Salmon calcitonin (s-CT) dose-dependently reduced the force of the contraction induced by naloxone in morphine incubated tissues, but did not modify the contraction induced by administration of acetylcholine or substance P in non-treated tissues. Therefore, the effect of s-CT in morphine incubated tissues may not be attributable to postsynaptic mechanisms, and an inhibitory modulation of the excitatory pathways triggered by naloxone would be suggested. In conclusion, s-CT is able to prevent the withdrawal sign in vitro.