Physiol Biochem Zool. 2023 May-Jun;96(3):167-176. doi: 10.1086/724688. Epub 2023 Apr 25.
AbstractThe dramatic decrease in heart rate (HR) during entrance into hibernation is not a mere response to the lowering of core body temperature () but a highly regulated fall, as the decrease in HR precedes the drop in . This regulated fall in HR is thought to be mediated by increased cardiac parasympathetic activity. Conversely, the sympathetic nervous system is thought to drive the increase of HR during arousal. Despite this general understanding, we lack temporal information on cardiac parasympathetic regulation throughout a complete hibernation bout. The goal of this study was to fill this gap in knowledge by using Arctic ground squirrels implanted with electrocardiogram/temperature telemetry transmitters. Short-term HR variability (root mean square of successive differences [RMSSD]), an indirect measure of cardiac parasympathetic regulation, was calculated in 11 Arctic ground squirrels. RMSSD, normalized as RMSSD/RR interval (RRI), increased fourfold during early entrance (from to , ). RMSSD/RRI peaked after HR dropped by over 90% and fell by 70%. Late entrance was delineated by a decline in RMSSD/RRI while continued to decrease. During arousal, HR started to increase 2 h before , with a concurrent decrease in RMSSD/RRI to a new minimum. As increased to a maximum during interbout arousal, HR declined, and RMSSD/RRI increased. These data suggest that activation of the parasympathetic nervous system initiates and regulates the HR decrease during entrance into hibernation and that withdrawal of parasympathetic activation initiates arousal. We conclude that cardiac parasympathetic regulation persists throughout all phases of a hibernation bout-a feature of the autonomic nervous system's regulation of hibernation that was not appreciated previously.
进入冬眠时心率（HR）的急剧下降不仅仅是对核心体温（Tb）降低的反应，而是一种高度调节的下降，因为 HR 的下降先于 Tb 的下降。这种 HR 的调节下降被认为是由心脏副交感神经活性的增加介导的。相反，交感神经系统被认为在唤醒期间驱动 HR 的增加。尽管有这种普遍的理解，但我们缺乏整个冬眠发作期间心脏副交感神经调节的时间信息。本研究的目的是通过使用植入心电图/温度遥测发射机的北极地松鼠来填补这一知识空白。短期 HR 变异性（连续差异的均方根 [RMSSD]），是心脏副交感神经调节的间接测量，在 11 只北极地松鼠中进行了计算。RMSSD 作为 RMSSD/心率（RRI）进行归一化，在早期进入时增加了四倍（从到）。RMSSD/RRI 在 HR 下降超过 90%和下降 70%后达到峰值。晚期进入的特征是 RMSSD/RRI 下降，而 Tb 继续下降。在唤醒期间，HR 在 Tb 开始增加前 2 小时开始增加，同时 RMSSD/RRI 下降到一个新的最小值。随着 Tb 在间歇唤醒期间增加到最大值，HR 下降，RMSSD/RRI 增加。这些数据表明，副交感神经系统的激活启动并调节进入冬眠时的 HR 下降，而副交感神经激活的撤回启动唤醒。我们得出结论，心脏副交感神经调节在冬眠发作的所有阶段都持续存在，这是以前未被认识到的自主神经系统调节冬眠的一个特征。
