Stalbovskiy Alexey O, Briant Linford J B, Paton Julian F R, Pickering Anthony E
School of Physiology & Pharmacology, Bristol Heart Institute, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 1TD, UK.
School of Physiology & Pharmacology, Bristol Heart Institute, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 1TD, UK Department of Engineering Mathematics, Merchant Venturers Building, Woodland Road, University of Bristol, Bristol, BS8 1UB, UK.
J Physiol. 2014 May 15;592(10):2215-36. doi: 10.1113/jphysiol.2014.270769. Epub 2014 Mar 24.
Sympathetic preganglionic neurones (SPNs) convey sympathetic activity flowing from the CNS to the periphery to reach the target organs. Although previous in vivo and in vitro cell recording studies have explored their electrophysiological characteristics, it has not been possible to relate these characteristics to their roles in cardiorespiratory reflex integration. We used the working heart-brainstem preparation to make whole cell patch clamp recordings from T3-4 SPNs (n = 98). These SPNs were classified by their distinct responses to activation of the peripheral chemoreflex, diving response and arterial baroreflex, allowing the discrimination of muscle vasoconstrictor-like (MVC(like), 39%) from cutaneous vasoconstrictor-like (CVC(like), 28%) SPNs. The MVC(like) SPNs have higher baseline firing frequencies (2.52 ± 0.33 Hz vs. CVC(like) 1.34 ± 0.17 Hz, P = 0.007). The CVC(like) have longer after-hyperpolarisations (314 ± 36 ms vs. MVC(like) 191 ± 13 ms, P < 0.001) and lower input resistance (346 ± 49 MΩ vs. MVC(like) 496 ± 41 MΩ, P < 0.05). MVC(like) firing was respiratory-modulated with peak discharge in the late inspiratory/early expiratory phase and this activity was generated by both a tonic and respiratory-modulated barrage of synaptic events that were blocked by intrathecal kynurenate. In contrast, the activity of CVC(like) SPNs was underpinned by rhythmical membrane potential oscillations suggestive of gap junctional coupling. Thus, we have related the intrinsic electrophysiological properties of two classes of SPNs in situ to their roles in cardiorespiratory reflex integration and have shown that they deploy different cellular mechanisms that are likely to influence how they integrate and shape the distinctive sympathetic outputs.
交感神经节前神经元（SPNs）将从中枢神经系统流向外周的交感神经活动传递至靶器官。尽管先前的体内和体外细胞记录研究已经探究了它们的电生理特性，但尚无法将这些特性与其在心肺反射整合中的作用联系起来。我们使用工作心脏-脑干标本，对T3-4节段的交感神经节前神经元（n = 98）进行全细胞膜片钳记录。这些交感神经节前神经元根据其对外周化学反射、潜水反射和动脉压力反射激活的不同反应进行分类，从而能够区分出类肌肉血管收缩型（MVC(like)，39%）和类皮肤血管收缩型（CVC(like)，28%）交感神经节前神经元。类肌肉血管收缩型交感神经节前神经元具有更高的基线放电频率（2.52±0.33 Hz，而类皮肤血管收缩型为1.34±0.17 Hz，P = 0.007）。类皮肤血管收缩型交感神经节前神经元具有更长的超极化后电位（314±36 ms，而类肌肉血管收缩型为191±13 ms，P < 0.001）和更低的输入电阻（346±49 MΩ，而类肌肉血管收缩型为496±41 MΩ，P < 0.05）。类肌肉血管收缩型的放电受呼吸调制，在吸气后期/呼气早期达到放电峰值，这种活动是由强直和呼吸调制的突触事件 barrage 产生的，鞘内注射犬尿氨酸可阻断这些事件。相比之下，类皮肤血管收缩型交感神经节前神经元的活动以提示缝隙连接耦合的节律性膜电位振荡为基础。因此，我们已经将两类交感神经节前神经元在原位的内在电生理特性与其在心肺反射整合中的作用联系起来，并表明它们采用了不同的细胞机制，这些机制可能会影响它们如何整合和塑造独特的交感神经输出。
