Potentiation of the halothane-cooling contractures of mammalian muscles by denervation

Denervation potentiated the cooling-induced contractures and the halothane-cooling contractures of isolated extensor digitorum longus and soleus muscles of the mouse. These effects were more striking in extensor digitorum longus than in soleus muscles. Significant increases in the peak amplitudes of the halothane-cooling contractures of both muscles and of the cooling contractures of soleus muscle were observed within 2 and 7 days of denervation. The potentiation of the contractures persisted for 90 days, the period of this study. Denervation (greater than 2 days) endowed extensor digitorum longus with the ability to generate cooling contractures in the absence of halothane. The rate of tension development of cooling-induced contractures in the absence or presence of halothane was significantly greater in denervated (2-90 days) than in innervated muscles. Denervation also reduced the effectiveness of procaine in inhibiting the halothane-cooling contractures. It is proposed that the potentiation of cooling-induced contractures in denervated muscles results primarily from an increase in the rate of efflux and in the quantity of Ca2+ released from the sarcoplasmic reticulum, upon cooling and (or) when challenged with halothane.