Effects of Motor Nerve Anesthesia and Tenotomy on Muscle Membrane Properties

Motor nerves to soleus muscles of rats were kept anesthetized for up to 7 days by applying solutions of lidocaine base or marcaine HCl. The anesthetic solutions were delivered from a subcutaneously located ALZA-minipump and reached the nerves through silastic cuffs. The ACh supersensitivity of muscles inactivated by nerve anesthesia for 3--7 days was comparable to that of muscles denervated for the same length of time. gm/gk (the ratio of total membrane conductance to the membrane K conductance) decreased from a normal value of 5--10 to less than two in 6--7 days, in anesthetic-inactivated and denervated muscles. The results were variable after 3 days of anesthesia. gm/gk of muscles which were tenotomized for 3 weeks was unchanged. The voltage-current curve for muscles kept in a solution containing 50 mM K propionate, which is steep at +50 mV, was less steep in denervated and anesthetic-inactivated, but not in tenotomized muscles, although atrophy was marked in all non-normal muscles.