Fratacci M D, Levame M, Rauss A, Atlan G
Institut National de la Santé et de la Recherche Médicale U296, Créteil, France.
Reprod Fertil Dev. 1996;8(3):399-407. doi: 10.1071/rd9960399.
The effects on the rat diaphragm of fatigue induced by low- and high-frequency stimulation (at 5 Hz for 1.5 min and 75 Hz for 1 min) were examined during postnatal development. Experiments were performed on isolated costal diaphragm strips. Before stimulation, twitch contraction time and half relaxation time were longest in the neonate and decreased significantly between weeks 1 and 6. Correspondingly, the specific twitch tension (corrected for cross-sectional area) increased progressively with age. After either low- or high-frequency fatigue, the force recovery was complete in 1- and 2-week-old rats, whereas the force production progressively decreased in older rats. In addition, the neonate diaphragm further enhanced its force selectively after high-frequency fatigue. It is concluded that the rat diaphragm is comparably resistant to fatigue during the early postnatal period, whether fatigue is induced by low- or by high-frequency stimulation. This suggests that postnatal changes in diaphragm contractile and fatigue properties may be related to changes in the process of force production. The possibility is discussed that a higher total muscle oxidative potential and the mechanisms leading to force potentiation in the neonate might explain the fatigue resistance.
在出生后发育过程中，研究了低频和高频刺激（5Hz刺激1.5分钟和75Hz刺激1分钟）诱导的疲劳对大鼠膈肌的影响。实验在分离的肋膈条上进行。刺激前，新生大鼠的抽搐收缩时间和半松弛时间最长，在出生后第1周和第6周之间显著缩短。相应地，比抽搐张力（根据横截面积校正）随年龄逐渐增加。在低频或高频疲劳后，1周龄和2周龄大鼠的力量恢复完全，而年龄较大的大鼠力量产生逐渐下降。此外，新生大鼠膈肌在高频疲劳后选择性地进一步增强其力量。结论是，无论疲劳是由低频还是高频刺激诱导，大鼠膈肌在出生后早期对疲劳具有相当的抵抗力。这表明膈肌收缩和疲劳特性的出生后变化可能与力量产生过程的变化有关。讨论了更高的总肌肉氧化潜能以及导致新生大鼠力量增强的机制可能解释疲劳抵抗的可能性。
