Complex cardiovascular actions of α-adrenergic receptors expressed in the nucleus tractus solitarii of rats
Complex cardiovascular actions of α-adrenergic receptors expressed in the nucleus tractus solitarii of rats
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DOI：
10.1113/expphysiol.2008.046490
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发表时间：
2009-07-01
影响因子：
2.7
通讯作者：
Maeda, Masanobu
中科院分区：
文献类型：
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作者：
Bhuiyan, Mohammad E. R.;Waki, Hidefumi;Maeda, Masanobu
虽然已知α(1)和α(2)肾上腺素能受体(ARs)均表达于孤束核(NTS)，但这些受体的功能意义仍未完全确立。在这项研究中，我们将α(1)-和α(2)-AR激动剂微量注射到乌拉坦麻醉的Wister大鼠的NTS，以研究它们的激活对心血管的影响。将α(1)-AR激动剂苯肾上腺素微量注射到压力敏感神经元占优势的区域(baro-NTS)，平均动脉压(MAP)和心率(HR)显著升高。然而，当在化疗敏感神经元主要分布的区域测试时，MAP和HR显著降低。NTS内预先注入非特异性α-AR拮抗剂酚妥拉明可抑制苯肾上腺素引起的心血管反应。相反，将α(2)-AR激动剂可乐定微量注射到正压核或化疗核均可降低MAP和HR；它们也可被α(2)-肾上腺素能拮抗剂育亨宾所抑制。此外，免疫组织化学证实，α(1)-Ars诱导的心血管反应可能由NTS神经元介导，而α(2)-Ars诱导的心血管反应可能由位于NTS压力敏感区和化学敏感区的星形胶质细胞介导。这些结果表明，在NTS表达的两种类型的α-AR可能通过调节压力感受器和化学感受器传入的输入信号而参与调节心血管内稳态；然而，刺激α(1)-AR产生的心血管反应在NTS内具有严格的位置特异性。
Although both alpha(1)- and alpha(2)-adrenergic receptors (ARs) are known to be expressed in the nucleus of the solitary tract (NTS), the functional significance of these receptors is still not fully established. In this study, we microinjected alpha(1)- and alpha(2)-AR agonists into the NTS of urethane-anaesthetized Wister rats to study the cardiovascular effects in response to their activation. When the alpha(1)-AR agonist phenylephrine was microinjected into the area where barosensitive neurons are dominantly located (baro-NTS), mean arterial pressure (MAP) and heart rate (HR) were significantly elevated. When tested in the area where chemosensitive neurons are dominantly located (chemo-NTS), however, MAP and HR were significantly decreased. Pretreatment with the non-specific alpha-AR antagonist phentolamine into the NTS inhibited the phenylephrine-induced cardiovascular responses. In contrast, microinjection of the alpha(2)-AR agonist clonidine into either the baro-NTS or the chemo-NTS decreased MAP and HR; they were also inhibited by the alpha(2)-adrenergic antagonist yohimbine. Moreover, we immunohistochemically identified that cardiovascular responses induced by alpha(1)-ARs may be mediated by NTS neurons while those induced by alpha(2)-ARs may be mediated by astrocytes located in the barosensitive and chemosensitive areas of the NTS. These results suggest that both types of alpha-AR expressed in the NTS may be involved in regulating cardiovascular homeostasis via modulation of input signals from baroreceptor and chemoreceptor afferents; however, cardiovascular responses produced by stimulation of alpha(1)-ARs are strictly location specific within the NTS.