局所虚血下における筋機能計測のための筋内挿入型プローブの開発

抄録

The muscular arterioles are locally dilated in muscle contraction, and glucose, lipids, etc. are supplied from the blood in a large amount. Simultaneously oxygen is also supplied, and an anaerobic condition of muscular tissue is avoided. The action potential that traveled from a motor nerve propagates to a myolemma. Simultaneously it propagates to a T-tubule and then Ca²⁺ is released from a sarcoplasmic reticulum by depolarization of the T-tubule. The local ischemia causes large effects, namely energy crisis, and also affects the electrical characteristic of the cell membrane, and it seems to be also concerned in the propagation velocity of action potential on the muscle fiber.
In this study, an intramuscular probe and measurement system were developed in order to measure muscle function under local ischemia. This probe is composed of a plastic optical fiber (500 μm in diameter) which measures blood flow and ten platinum fine electrodes (50 μm in diameter) for the action potential measurement. The distance between each electrode pair is about 170 μm. The probe is inserted in cannula of1.6 mm in diameter. Ten electrical buffer circuits are installed in the grip of the probe.
Animal tests using rats were carried out in order to verify the developed probe and system. In gastrocnemius of the rat, the action potential waveform and blood flow were measured using this probe. In the experiment, tibial nerve was stimulated electrically and the action potentials were recorded. Their signals were sampled at 30 kHz and recorded for 10 ms. The amplitudes of potentials were about ±1.5 mV and they remained for about 5 ms. The latency of waves is about 1.5 ms and the phase between the two waves is about 0.25 ms. The similarity of both waves was examined, using a cross correlation function during the measurement. The distance between two electrodes is 517.6 μm and the propagation velocity was about 2.1 m/s.
In the other experiment, a popliteal artery was ligated. With the progress of the ischemia, the action potential propagation velocity, which was calculated from the potential waveforms in the two electrodes, gradually decreased after the ligation. In all cases of several experiments, the propagation velocity decreased. A biosensor by which biochemistry markers etc. can be measured simultaneously will be built in a future measurement probe.