Effects of calcitonin-induced hypocalcemia on the neuromuscular and cardiovascular depressive actions of kanamycin in anesthetized and conscious rats.

It was examined whether calcitonin (CT)-induced hypocalcemia could modify the pharmacological actions of kanamycin sulfate (KM). CT produced a dose dependent and long-lasting hypocalcemia in urethane anesthetized and conscious rats. In anesthetized rats, KM infusion depressed the indirectly elicited contractions of the tibialis anterior muscle (MC), mean arterial pressure (AP), heart rate (HR) and respiratory rate. CT did not influence the stability of the above parameters and slightly modified the neuromuscular depression of KM. In conscious rats, KM infusion produced spontaneous and complete head drop, loss of corneal reflex, respiratory arrest and also depressed AP and HR. Much higher doses of KM were required to induce the same pharmacological actions in conscious than in anesthetized rats. CT dose-dependently potentiated the pharmacological actions of KM. A highly significant linear correlation between the serum total calcium levels and the KM dose inducing spontaneous head drop was observed. These data indicate that, in conscious rats, the actions of KM are dependent on the serum calcium levels. In the same experimental conditions, neither CT-induced hypocalcemia nor anesthesia did modify significantly the pharmacological actions of d-tubocurarine.