Zabka A G, Behan M, Mitchell G S
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA.
J Physiol. 2001 Mar 1;531(Pt 2):509-14. doi: 10.1111/j.1469-7793.2001.0509i.x.
Long term facilitation (LTF) is a serotonin-dependent augmentation of respiratory motor output (phrenic and hypoglossal) following episodic hypoxia. Since ageing influences respiratory control mechanisms and serotonergic function, we tested the hypothesis that LTF decreases with age in male rats. Young (3-4 month) and aged (13 month) male Sprague-Dawley rats were anaesthetized with urethane, vagotomized, paralysed and pump ventilated. Integrated phrenic and hypoglossal (XII) nerve activities were measured before (baseline), during and for 60 min after three 5 min episodes of isocapnic hypoxia (Pa,O2 35-45 mmHg) separated by 5 min of hyperoxia (Pa,O2 > 150 mmHg). In young rats, LTF was observed as an augmentation in peak integrated phrenic (n = 8) and XII (n = 7) amplitudes following episodic hypoxia (56 +/- 14 and 73 +/- 16 % (means +/- S.E.M.) at 60 min post-hypoxia, respectively; both P < 0.05). In aged rats, LTF was significantly increased compared to baseline in phrenic (25 +/- 8 % at 60 min, P < 0.05), but not in XII (4 +/- 7 %, P > 0.05) motor output. LTF was significantly greater in young than in aged rats in both motor outputs (P < 0.05). Decreased phrenic and XII LTF suggests that serotonergic modulation of respiratory motor output decreases in ageing male rats. We speculate that decreased serotonergic modulation may contribute to age-related breathing disorders.
长期易化（LTF）是指在间歇性低氧后，5-羟色胺依赖性的呼吸运动输出（膈神经和舌下神经）增强。由于衰老会影响呼吸控制机制和5-羟色胺能功能，我们检验了雄性大鼠中LTF随年龄增长而降低的假说。将年轻（3-4个月）和老年（13个月）雄性Sprague-Dawley大鼠用乌拉坦麻醉，切断迷走神经，使其麻痹并进行泵通气。在三次5分钟等碳酸血症性低氧发作（动脉血氧分压35-45 mmHg）之前（基线）、期间及之后60分钟测量膈神经和舌下神经（XII）的综合神经活动，每次低氧发作之间间隔5分钟的高氧（动脉血氧分压>150 mmHg）。在年轻大鼠中，观察到LTF表现为间歇性低氧后膈神经（n = 8）和舌下神经（n = 7）综合峰值幅度增强（低氧后60分钟时分别为56±14%和73±16%（平均值±标准误）；P均<0.05）。在老年大鼠中，膈神经运动输出的LTF与基线相比显著增加（60分钟时为25±8%，P<0.05），但舌下神经运动输出未增加（4±7%，P>0.05）。在两种运动输出中，年轻大鼠的LTF均显著高于老年大鼠（P<0.05）。膈神经和舌下神经LTF降低表明，衰老雄性大鼠中呼吸运动输出的5-羟色胺能调节减弱。我们推测，5-羟色胺能调节减弱可能导致与年龄相关的呼吸障碍。
