[Effect of retroauricular galvanic stimulation on muscle atrophy in the unweighted rat hindlimb]

Hindlimb unweighting in the rat may serve as an experimental model simulating muscle atrophy under weightlessness. As a preventive measure, retroauricular galvanic stimulation was delivered to the unweighted rat hindlimb and the weights of the bilateral soleus and gastrocnemius muscles were compared. Wistar rats, with unweighted hindlimbs, were divided into two groups; the control group which received no galvanic stimulation and a galvanically stimulated group which received galvanic stimulation (bipolar biauricular, 1 mA in intensity, 500 msec in duration, 1 Hz in frequency) for one hour twice a day for 7 days using an electronic stimulator made by NIHON-KODEN (MODEL SEN-1101). The weights of the soleus and gastrocnemius muscles on both sides were measured in each group using a balance (METTLER AT201). The results were as follows: 1. Muscle weights in the galvanically stimulated group were greater than those in the control group. 2. A statistically significant difference between right and left soleus muscle weights was obtained in the galvanically stimulated group (P < 0.01). 3. We found no significant difference between the two sides in the weights of gastrocnemius muscles. It is presumed that retroauricular galvanic stimulation exerts some influence, not only on vestibular organs, but also on hindlimb muscles through the lateral vestibulo-spinal tract and, in addition, through the spinal motor neuron. Therefore, we speculate that galvanic stimulation might prevent atrophy of the unweighted hindlimb muscle.