CALCITONIN INCREASES THE INHIBITORY EFFECT OF OPIOIDS IN GUINEA-PIG ILEUM

1. The relationship between salmon calcitonin (S-CT) and opioid system was studied in isolated guinea-pig ileum. 2. Addition of S-CT (0.1 to 1.6 U/ml) to the organ bath did not modify the amplitude of the contractile response induces by electrical stimulation. 3. However, when tissues were incubated 30 min with S-CT (0.1 U/ml), the inhibitory effect of the release of endogenous opioids, met-enkephalin (1-mu-M) and morphine (0.2-mu-M) was significantly increased. 4. Our results suggest that some of the analgesic effects of S-CT could be attributed to an up-regulation of the opioid receptors.