Abstract：
In this review, we explore the inconsistencies in the data and gaps in our knowledge that exist in what is currently known regarding gill chemosensors which drive the cardiorespiratory reflexes in fish. Although putative serotonergic neuroepithelial cells (NEC) dominate the literature, it is clear that other neurotransmitters are involved (adrenaline, noradrenaline, acetylcholine, purines, and dopamine). And although we assume that these agents act on neurons synapsing with the NECs or in the afferent or efferent limbs of the paths between chemosensors and central integration sites, this process remains elusive and may explain current discrepancies or species differences in the literature. To date it has been impossible to link the distribution of NECs to species sensitivity to different stimuli or fish lifestyles and while the gills have been shown to be the primary sensing site for respiratory gases, the location (gills, oro-branchial cavity or elsewhere) and orientation (external/water or internal/blood sensing) of the NECs are highly variable between species of water and air breathing fish. Much of what has been described so far comes from studies of hypoxic responses in fish, however, changes in CO2, ammonia and lactate have all been shown to elicit cardio-respiratory responses and all have been suggested to arise from stimulation of gill NECs. Our view of the role of NECs is broadening as we begin to understand the polymodal nature of these cells. We begin by presenting the fundamental picture of gill chemosensing that has developed, followed by some key unanswered questions about gill chemosensing in general.
摘要：
在这次审查中,我们探讨了目前已知的有关g化学传感器驱动鱼类心肺反射的数据不一致和知识空白。尽管推定的5-羟色胺能神经上皮细胞（NEC）在文献中占主导地位，很明显，其他神经递质也参与其中(肾上腺素，去甲肾上腺素,乙酰胆碱，嘌呤,和多巴胺）。尽管我们假设这些试剂作用于与NEC突触的神经元，或者作用于化学传感器和中央整合位点之间路径的传入或传出肢体，这个过程仍然难以捉摸，可以解释文献中当前的差异或物种差异。迄今为止，还不可能将NEC的分布与物种对不同刺激或鱼类生活方式的敏感性联系起来，尽管已证明g是呼吸气体的主要感应部位，位置(g，NEC的口支气管腔或其他地方）和方向（外部/水或内部/血液感应）在水和呼吸空气的鱼类之间变化很大。到目前为止，大部分描述来自鱼类缺氧反应的研究，然而,CO2，氨和乳酸的变化都被证明会引起心肺反应，并且所有变化都被认为是由gNEC的刺激引起的。随着我们开始了解这些细胞的多模态性质，我们对NEC的作用的看法正在扩大。我们首先介绍已经发展起来的ill化学传感的基本情况，其次是一些关于一般的ill化学传感的关键未解决的问题。
