PLoS ONE：裸鼢鼠为减轻人类疼痛提供研究思路

除了裸鼢鼠（naked mole-rat）之外，其他哺乳动物包括人都无法在酸性环境中生存。美国伊利诺伊大学的研究人员对这一现象进行了研究，相关论文发表在PLoS ONE上。

在非常拥挤的非洲裸鼢鼠的洞穴中，二氧化碳的浓度高到对于任何别的哺乳动物都是有毒，空气的酸度也很高，而裸鼢鼠却可忍受这样不利的环境。

这项研究的领导者Thomas Park说，这或许为缓解其他动物和人的疼痛提供线索，因为绝大多数的挥之不去的疼痛都是由受伤组织的酸化造成的。伤口酸化是难以避免的，研究在酸性环境中无疼痛感的动物应该可以找到缓解人类疼痛的方法。

酸性气体可激活哺乳动物鼻子中的神经纤维，进而激活脑干中的三叉神经核，而后产生保护机体的生理和行为反应，如分泌黏液、擦鼻子、避开酸性气体等。

研究者将裸鼢鼠放在有些区域有酸性气体的笼子中，记录它们在不同区域所待的时间。与之对照的是大鼠、小鼠及与裸鼢鼠亲缘很近但喜好舒适环境的一种鼢鼠。结果发现，裸鼢鼠在有酸性气体和无酸性气体的区域所待的时间一样长，但对照组的动物都避开酸性气体。

研究者通过测量一种蛋白质c-Fos的量将生理反应过程量化，c-Fos是神经活动的直接标志物，它往往在激活的神经细胞中表达。而在裸鼢鼠中并未检测到三叉神经核中的c-Fos的活性，对照组的三叉神经核却是高度激活的。

编译自Naked mole-rats may hold clues to pain relief

doi:10.1371/journal.pone.0045060
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Blunted Behavioral and C Fos Responses to Acidic Fumes in the African Naked Mole-Rat

Pamela Colleen LaVinka¤, Thomas J. Park*

Acidosis in the skin triggers activation of pain pathways and behaviors indicative of pain in vertebrates. The exception is the naked mole-rat, the only known vertebrate to show physiological and behavioral insensitivity to acid pain in the skin. The goal of the present study was to determine behavioral and physiological responses of this species to airborne acidic fumes, which would be expected to affect the trigeminal pain pathway in other species. Behaviorally, naked mole-rats did not avoid fumes from moderately high concentrations of acetic acid (10 and 20%), and c Fos labeling showed no increase in activity in the trigeminal nuclei and nucleus tractus solitarius. In contrast, these concentrations triggered behavioral aversion and increased Fos activity in other laboratory rodents. For a very high concentration of acetic acid (50%), naked mole-rats showed significant avoidance behavior and increased Fos labeling in the nucleus tractus solitarius caudal region, which receives vagal chemosensory information. However, there was no increase in trigeminal labeling, and in fact, activity significantly decreased. This pattern is opposite of that associated with another irritant, ammonia fumes, which elicited an increase in trigeminal but not nucleus tractus solitarius Fos labeling, and no behavioral avoidance. Behavioral avoidance of acidic fumes, but no increased labeling in the trigeminal pain nucleus is consistent with the notion of adaptations to blunt acid pain, which would be advantageous for naked mole-rats as they normally live under chronically high levels of acidosis-inducing CO2.