CNS and Na-Pump in Situ Muscle

Abstract

Recently, it has been demonstrated that the high [Na]_i and low [K]_i levels in in sit. soleus muscle of the hypokalemic rat are the result of the direct inhibition of ouabain-sensitive Na-pump not by low plasma K⁺ level but CNS (Akaike, 1979; 1980). Such a CNS-inhibition on Na-pump was eliminated by sectioning the peripheral nerve to soleus or by spinal transection at the cervical level. The activation of Na-pump following nerve section was not affected by pretreatment with curare, but was completely inhibited by the electrical stimulation (rectangular pulse with the duration of 0.05 msec at 10 Hz) of the sectioned nerve in the curarized hypokalemic rat. The muscle Na-pump was also activated in the presence of several adrenergic α-blockers without nerve section while β-blockers had no effects on the pump.