Ernsberger P, Kou Y R, Prabhakar N R
Department of Nutrition, Case Western Reserve School of Medicine, Cleveland, OH 44106-4906, USA.
Respir Physiol. 1998 Jun;112(3):239-51. doi: 10.1016/s0034-5687(98)00021-8.
The carotid body is influenced by many neurotransmitter receptors. A novel receptor specific for imidazolines has been implicated in cardiorespiratory regulation in the brain. To test for both I1-imidazoline and alpha2-adrenergic receptors, which also recognize imidazolines, specific [125I]p-iodoclonidine binding to carotid body membranes was characterized. The specific alpha2-agents epinephrine (100 microM) or SK&F 86466 (10 microM) inhibited only a portion of specific [125I]p-iodoclonidine binding in both cat and rabbit carotid bodies, indicating the presence of I1-imidazoline as well as alpha2-adrenergic sites. The distribution of [125I]p-iodoclonidine binding sites was visualized autoradiographically. The cat carotid body was intensely labeled by [125I]p-iodoclonidine, with both I1-imidazoline and alpha2-adrenergic sites expressed. The relevance of I1-imidazoline receptors in modulation of chemosensory discharge was determined in seven cats after alpha2-adrenergic blockade. Clonidine (100 microg/kg) facilitated chemosensory activity particularly under hypoxia. We conclude that I1-imidazoline receptors are expressed within the carotid body and may potentiate chemosensory discharge, in contrast to the inhibitory action of alpha2-adrenergic receptors.
颈动脉体受多种神经递质受体的影响。一种对咪唑啉特异的新型受体与大脑中的心肺调节有关。为了检测同时识别咪唑啉的I1-咪唑啉受体和α2-肾上腺素能受体，对特异性[125I]对碘氯苯胍与颈动脉体膜的结合进行了表征。特异性α2-制剂肾上腺素（100微摩尔）或SK&F 86466（10微摩尔）仅抑制猫和兔颈动脉体中特异性[125I]对碘氯苯胍结合的一部分，表明存在I1-咪唑啉以及α2-肾上腺素能位点。通过放射自显影观察[125I]对碘氯苯胍结合位点的分布。猫的颈动脉体被[125I]对碘氯苯胍强烈标记，同时表达I1-咪唑啉和α2-肾上腺素能位点。在七只猫进行α2-肾上腺素能阻断后，确定了I1-咪唑啉受体在调节化学感受性放电中的相关性。可乐定（100微克/千克）促进化学感受性活动，尤其是在低氧条件下。我们得出结论，与α2-肾上腺素能受体的抑制作用相反，I1-咪唑啉受体在颈动脉体内表达并可能增强化学感受性放电。
