Chemoreceptor nerve excitation may not be proportional to catecholamine secretion
Chemoreceptor nerve excitation may not be proportional to catecholamine secretion
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DOI：
10.1152/jappl.1996.81.2.657
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发表时间：
1996-08-01
影响因子：
3.3
通讯作者：
Donnelly, DF
中科院分区：
文献类型：
--
作者：
Donnelly, DF
颈动脉体血管球细胞分泌儿茶酚胺的增强被认为在介导外周化学受体对缺氧的反应中起重要作用。为了验证这一假设，儿茶酚胺分泌与神经活动之间的关系在重复缺氧刺激和儿茶酚胺消耗后用利血平进行了检查。单纤维传入神经活动的测量与游离组织儿茶酚胺的估计使用nafon涂层碳纤维微电极放置在体外大鼠颈动脉体。在重复刺激（持续缺氧1分钟；最低点Po-2 = 0 Torr，每200秒重复一次）期间，定量基线和受刺激的神经和儿茶酚胺水平。峰值受刺激的儿茶酚胺从第一次刺激的26.4 +/- 2.6 μ M逐渐下降到第五次刺激的7.5 +/- 0.9 μ M (n = 15)，但峰值神经活动受到的影响要小得多（第一次试验23.0 +/- 1.9 Hz；第五次试验19.9 +/- 1.4 Hz）。在重复缺氧刺激前暴露于中度缺氧（类似于80托）产生的儿茶酚胺水平与重复缺氧时获得的水平相当，但峰值神经活动明显更少（22.5 +/- 3.4 Vs. 12.7 +/- 2.1 Hz）。利血平（1 mg/100 g）预处理导致低氧诱导的儿茶酚胺平均反应（1.4 +/- 0.3 μ M, n = 9）大幅降低，但峰值神经活动与未处理的对照组没有差异。这些结果表明颈动脉体儿茶酚胺分泌和神经活动之间的独立性，表明神经兴奋至少部分是通过独立于颗粒分泌的途径介导的。
Enhanced catecholamine secretion from the carotid body glomus cells is hypothesized to play an essential role in mediating the peripheral chemoreceptor response to hypoxia. To test aspects of this hypothesis, the relationship between catecholamine secretion and nerve activity was examined during repetitive hypoxia stimuli and after catecholamine depletion with reserpine. Single-fiber afferent nerve activity was measured along with an estimate of free tissue catecholamine by using Nafion-coated carbon-fiber microelectrodes placed in rat carotid bodies in vitro. Baseline and stimulated nerve and catecholamine levels were quantified during repetitive stimulation (anoxia of 1-min duration; Po-2 = 0 Torr at nadir, repeated each 200 s). Peak stimulated catecholamine progressively decreased from 26.4 +/- 2.6 mu M for the first stimulus to 7.5 +/- 0.9 mu M for the fifth stimulus (n = 15), but peak nerve activity was much less affected (23.0 +/- 1.9 Hz, first trial; 19.9 +/- 1.4 Hz, fifth trial). An exposure to moderate hypoxia (similar to 80 Torr) before the repetitive anoxia stimuli produced catecholamine levels comparable to those obtained during repetitive anoxia, but peak nerve activity was significantly less (22.5 +/- 3.4 Vs. 12.7 +/- 2.1 Hz). Pretreatment with reserpine (1 mg/100 g) resulted in a large reduction in the average hypoxia-induced catecholamine response (1.4 +/- 0.3 mu M, n = 9), but peak, nerve activity was not different from nontreated controls. These results demonstrate an independence between carotid body catecholamine secretion and nerve activity, suggesting that nerve excitation is, at least, partially mediated through pathways independent of granule secretion.