Oddi's sphincter spasm in hypocalcaemia of dogs.

1. Decreases of serum calcium concentration in dogs lead to increased basal tone of Oddi's sphincter in the employed experimental model. 2. This effect is independent of the agent used for decreasing the serum calcium level. 3. Spasmolysis was observed immediately after the injection of CaCl2. CaCl2 alone, however, had no effect in "normocalcaemic" animals. 4. Local decrease of calcium level plays no significant role in the sphincter spasm. It is suggested that the spasm is elicited by increased smooth muscle excitability as a consequence of the hypocalcaemic state prevailing in the body.