Boucher M, Chassaing C, Chapuy E, Lorente P
INSERM U. 195, Faculty of Medicine, Clermont-Ferrand, France.
J Cardiovasc Pharmacol. 1996 Dec;28(6):842-7. doi: 10.1097/00005344-199612000-00015.
This work (a) provides evidence for hysteresis in the atrial effective refractory period (AERP) in the conscious dog; (b) studies the main stimulation parameters that may affect this phenomenon; and (c) evaluates the influence of the autonomic nervous system. AERP was measured by the extrastimulus method in the conscious dog with chronic atrioventricular block (n = 6) during the increasing and decreasing phases of an S1S2 fixed protocol. AERP was longer during the increasing phase than during the decreasing phase, thus demonstrating hysteresis, calculated as the difference between the two values. Hysteresis was greater with an S1S1 basic cycle length of 300 ms than with a basic cycle length of 400 ms, 9 +/- 0.9, and 7 +/- 0.9 ms, respectively. It was also greater with trains of six basic cycles before each extrastimulus S2 than with trains of 12 basic cycles, 9 +/- 0.9 and 7 +/- 1.0 ms, respectively. Suppression of vagal tone with atropine reduced hysteresis from 8 +/- 0.6 to 4 +/- 0.6 ms, whereas suppression of cardioaccelerator tone with propranolol increased it from 9 +/- 0.9 to 14 +/- 1.2 ms. These data were confirmed by the neostigmine-induced increase in hysteresis from 8 +/- 0.8 to 11 +/- 0.8 ms and the isoproterenol-induced decrease in hysteresis from 9 +/- 0.6 to 4 +/- 0.4 ms. Overall, these results provide evidence for a hysteresis effect in the AERP in the conscious dog that is stimulation frequency-dependent and modulated by the autonomic nervous system with permanent increase by vagal tone and decrease by cardioaccelerator tone.
本研究 (a) 为清醒犬心房有效不应期 (AERP) 中的滞后现象提供了证据；(b) 研究了可能影响该现象的主要刺激参数；(c) 评估了自主神经系统的影响。采用额外刺激法，在慢性房室传导阻滞的清醒犬 (n = 6) 中，于S1S2固定方案的递增和递减阶段测量AERP。AERP在递增阶段比递减阶段更长，从而证明了滞后现象，其计算为两个值之间的差异。S1S1基础周期长度为300 ms时的滞后现象比基础周期长度为400 ms时更大，分别为9±0.9和7±0.9 ms。每次额外刺激S2前有六个基础周期的序列时的滞后现象也比有12个基础周期序列时更大，分别为9±0.9和7±1.0 ms。用阿托品抑制迷走神经张力可使滞后现象从8±0.6 ms降至4±0.6 ms，而用普萘洛尔抑制心脏加速神经张力则使其从9±0.9 ms增至14±1.2 ms。新斯的明使滞后现象从8±0.8 ms增至11±0.8 ms，异丙肾上腺素使滞后现象从9±0.6 ms降至4±0.4 ms，这些数据证实了上述结果。总体而言，这些结果为清醒犬AERP中的滞后效应提供了证据，该效应依赖于刺激频率，并由自主神经系统调节，迷走神经张力使其持续增加，心脏加速神经张力使其降低。
