Webber C L, Pleschka K
Pflugers Arch. 1984 Sep;402(1):10-7. doi: 10.1007/BF00584825.
A technique of reversible cold blockade was applied in decerebrate and vagotomized rabbits that were immobilized and artificially ventilated to study the modulation of spontaneous respiratory rhythms. Respiratory discharges were recorded from vagal and phrenic efferents before and during cold blockade at the second cervical segment (C2) with a coolant-circulated thermode (-15 degrees C). Measurement of the cooling profile demonstrated that there was significant hypothermia in the regions of the phrenic nucleus (+25 degrees C) and obex of the medulla (+26 degrees C). Arterial pressure was maintained by continual norepinephrine infusion, end-tidal carbon dioxide tension was held at hypercapnic levels, and rectal temperature was regulated near 38 degrees C. The cold blockade of descending respiratory drives to the cervical phrenic nucleus inhibited the spontaneous activity in the phrenic nerve for more than 90 min. Phrenic activity could be induced by the intravenous injection of strychnine, but not doxapram, although this was not of respiratory quality. These results show that in the absence of descending and pharmacologic drives, but in the presence of phrenic hypothermia, spinalized rabbits are incapable of generating rhythmic patterns of discharge. C2 cold blockade also significantly slowed the spontaneous central respiratory rhythm with no change in integrated vagal amplitude, presumably due to a direct cooling effect on brainstem oscillators for breathing.
一种可逆性冷阻断技术应用于去大脑和切断迷走神经的家兔，这些家兔被固定并进行人工通气，以研究对自发性呼吸节律的调节。在第二颈椎节段（C2）用冷却剂循环的热电极（-15℃）进行冷阻断之前和期间，记录迷走神经和膈神经传出纤维的呼吸放电。冷却剖面测量表明，膈神经核区域（+25℃）和延髓闩部（+26℃）存在明显的体温过低。通过持续输注去甲肾上腺素维持动脉血压，将呼气末二氧化碳张力维持在高碳酸血症水平，并将直肠温度调节至接近38℃。对颈段膈神经核的下行呼吸驱动进行冷阻断可抑制膈神经的自发活动超过90分钟。静脉注射士的宁可诱发膈神经活动，但多沙普仑不能诱发，尽管这不是呼吸性质的。这些结果表明，在没有下行和药物驱动但存在膈神经体温过低的情况下，脊髓横断的家兔无法产生节律性放电模式。C2冷阻断还显著减慢了自发性中枢呼吸节律，迷走神经综合振幅无变化，这可能是由于对脑干呼吸振荡器的直接冷却作用。
