Delay R J, Kinnamon S C, Roper S D
Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA.
J Neurophysiol. 1997 May;77(5):2515-24. doi: 10.1152/jn.1997.77.5.2515.
Necturus taste buds contain two primary cell types: taste receptor cells and basal cells. Merkel-like basal cells are a subset of basal cells that form chemical synapses with taste receptor cells and with innervating nerve fibers. Although Merkel-like basal cells cannot interact directly with taste stimuli, recent studies have shown that Merkel-like basal cells contain serotonin (5-HT), which may be released onto taste receptor cells in response to taste stimulation. With the use of whole cell voltage clamp, we examined whether focal applications of 5-HT to isolated taste receptor cells affected voltage-activated calcium current (I(Ca)). Two different effects were observed. 5-HT at 100 microM increased I(Ca) in 33% of taste receptor cells, whereas it decreased I(Ca) in 67%. Both responses used a 5-HT receptor subtype with a pharmacological profile similar to that of the 5-HT1A receptor, but the potentiation and inhibition of I(Ca) by 5-HT were mediated by two different second-messenger cascades. The results indicate that functional subtypes of taste receptor cells, earlier defined only by their sensitivity to taste stimuli, may also be defined by their response to the neurotransmitter 5-HT and suggest that 5-HT released by Merkel-like basal cells could modulate taste receptor function.
味觉受体细胞和基底细胞。默克尔样基底细胞是基底细胞的一个子集，它们与味觉受体细胞以及支配神经纤维形成化学突触。尽管默克尔样基底细胞不能直接与味觉刺激相互作用，但最近的研究表明，默克尔样基底细胞含有血清素（5-羟色胺，5-HT），味觉刺激时血清素可能释放到味觉受体细胞上。我们使用全细胞电压钳技术，研究了向分离出的味觉受体细胞局部施加5-HT是否会影响电压激活钙电流（I(Ca)）。观察到两种不同的效应。100微摩尔的5-HT使33%的味觉受体细胞的I(Ca)增加，而使67%的味觉受体细胞的I(Ca)降低。两种反应均使用了一种药理学特性与5-HT1A受体相似的5-HT受体亚型，但5-HT对I(Ca)的增强和抑制是由两种不同的第二信使级联介导的。结果表明，味觉受体细胞的功能亚型，此前仅根据它们对味觉刺激的敏感性来定义，也可能根据它们对神经递质5-HT的反应来定义，这表明默克尔样基底细胞释放的5-HT可能调节味觉受体功能。
