DOES ELECTRICAL-STIMULATION OF THE SCIATIC-NERVE PREVENT SUSPENSION-INDUCED CHANGES IN RAT HINDLIMB BONES

Osteoporosis due to mineral loss is a major health problem resulting f rom long-term spaceflight. The development of a suitable countermeasur e is essential because an advanced decrease in bone density could be i rreversible. Therefore the current study was performed to test our hyp othesis that the loading of bones by electrical stimulation-induced mu scle contraction may prevent the mineral loss caused by gravitational unloading and bone growth will be maintained. During 10 d of hindlimb suspension, electrical stimulation at 1, 50, or 100 Hz was administere d through the left sciatic nerve at the gluteal region of rats with ap proximately 300g body weight. The dry weight, mineral content, and min eral density in hindlimb bones were analyzed. The dry weight and miner al content of femur and tibia-fibula in hindlimb-suspended rats tended to be less than in the age-matched cage controls. However, these detr imental effects were prevented by stimulation at 50 and 100 Hz. A posi tive effect of stimulation was seen even in the nonstimulated limb, al though greater effect was induced in the stimulated limb. It is sugges ted that loading by stimulation-induced muscle contraction at higher f requencies is beneficial for the maintenance of bone growth or the pre vention of mineral loss, or both, during hindlimb suspension in rats.