Merkel disc is a serotonergic synapse in the epidermis for transmitting tactile signals in mammals
Merkel disc is a serotonergic synapse in the epidermis for transmitting tactile signals in mammals
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DOI：
10.1073/pnas.1610176113
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发表时间：
2016-09-13
影响因子：
11.1
通讯作者：
Gu, Jianguo G.
中科院分区：
文献类型：
--
作者：
Chang, Weipang;Kanda, Hirosato;Gu, Jianguo G.
感觉系统的进化使哺乳动物发展出复杂的触觉末端器官，以完成复杂的感觉任务，包括社会互动、环境探索和触觉识别。梅克尔盘是由梅克尔细胞（Merkel cells, MCs）和a-传入末梢组成的一种主要的触觉末梢器官，在哺乳动物的指尖、触觉丘和须毛囊中大量存在。默克尔圆盘对物体的物理特征，如纹理、形状和边缘有很高的触觉敏锐度。梅克尔盘的触觉功能机制尚不清楚MCs如何将触觉信号传递到导致触觉的A -传入末梢。利用小鼠须毛囊，我们发现触觉刺激被MCs转导成兴奋信号，从而触发MCs的囊性血清素释放。我们发现嗜离子性和代谢性5-羟色胺（5-HT）受体均在须A β -传入末梢表达，并且它们被MCs释放的5-羟色胺激活后启动β -传入脉冲。此外，我们证明了这些嗜离子性和代谢性5-羟色胺受体具有协同作用，这对电生理和行为触觉反应都至关重要。这些发现阐明了默克尔盘是一种独特的位于表皮的血清素能突触，在触觉传递中起关键作用。表皮5 -羟色胺能突触可能在感觉功能障碍中具有重要的临床意义，例如糖尿病、炎症性疾病和化疗患者的触觉敏感性丧失和触觉异常性痛。它也可能暗示了由娱乐性药物引起的夸张的触觉，这些药物作用于血清素能突触。
The evolution of sensory systems has let mammals develop complicated tactile end organs to enable sophisticated sensory tasks, including social interaction, environmental exploration, and tactile discrimination. The Merkel disc, a main type of tactile end organ consisting of Merkel cells (MCs) and A beta-afferent endings, are highly abundant in fingertips, touch domes, and whisker hair follicles of mammals. The Merkel disc has high tactile acuity for an object's physical features, such as texture, shape, and edges. Mechanisms underlying the tactile function of Merkel discs are obscured as to how MCs transmit tactile signals to A beta-afferent endings leading to tactile sensations. Using mouse whisker hair follicles, we show herein that tactile stimuli are transduced by MCs into excitatory signals that trigger vesicular serotonin release from MCs. We identify that both ionotropic and metabotropic 5-hydroxytryptamine (5-HT) receptors are expressed on whisker A beta-afferent endings and that their activation by serotonin released from MCs initiates A beta-afferent impulses. Moreover, we demonstrate that these ionotropic and metabotropic 5-HT receptors have a synergistic effect that is critical to both electrophysiological and behavioral tactile responses. These findings elucidate that the Merkel disc is a unique serotonergic synapse located in the epidermis and plays a key role in tactile transmission. The epidermal serotonergic synapse may have important clinical implications in sensory dysfunctions, such as the loss of tactile sensitivity and tactile allodynia seen in patients who have diabetes, inflammatory diseases, and undergo chemotherapy. It may also have implications in the exaggerated tactile sensations induced by recreational drugs that act on serotoninergic synapses.