Cervero F
Baillieres Clin Gastroenterol. 1988 Jan;2(1):183-99. doi: 10.1016/0950-3528(88)90027-9.
The only non-general sensation that can be evoked from the gastrointestinal (GI) tract is that of pain ranging from mild discomfort to intense pain. However, in certain regions of the gut, such as the rectum and gastro-oesophagus, the feeling of pain can be preceded by non-painful sensations of distension at lower stimulus intensities. GI pain is often dull, aching, ill-defined and badly localized. In some cases, GI pain is projected to areas of the body away from the originating viscus ('referred' pain). These properties indicate that the representation of internal organs within the central nervous system is very imprecise. Behavioural, neurophysiological and clinical evidence shows that most forms of GI pain are mediated by activity in visceral afferent fibres running in sympathetic nerves and that the afferent innervation of the gut mediated by parasympathetic nerves is not primarily concerned with the signalling and transmission of GI pain. As for the encoding mechanism of the peripheral sensory receptor in the gut, there is evidence for the existence of specific visceral nociceptors in some locations (e.g. the biliary system) and for the existence of non-specific 'intensity' type receptors in other locations (e.g. the colon). In any case, the actual number of nociceptive afferent fibres in the gut is very small and this explains why large areas of the GI tract appear to be insensitive or require considerable stimulation before giving rise to painful sensations. The few nociceptive afferents contained in sympathetic nerves can excite many second order neurones in the spinal cord which in turn generate extensive divergence within the spinal cord and brain stem, sometimes involving long supraspinal loops. Such a divergent input can activate many different systems, motor and autonomic as well as sensory, and thus trigger the general reactions that are characteristic of visceral nociception: a diffuse and ill-localized pain sometimes referred to somatic areas, and autonomic and somatic reflexes that result in prolonged motor activity.
胃肠道（GI）能引发的唯一非一般性感觉是疼痛，其程度从轻微不适到剧痛不等。然而，在肠道的某些区域，如直肠和胃食管，在较低刺激强度下，疼痛感觉之前可能会出现非疼痛性的扩张感。胃肠道疼痛通常是钝痛、隐痛、界限不清且定位不佳。在某些情况下，胃肠道疼痛会投射到身体远离起始内脏的部位（“牵涉”痛）。这些特性表明中枢神经系统内对内脏器官的表征非常不精确。行为学、神经生理学和临床证据表明，大多数形式的胃肠道疼痛是由交感神经中走行的内脏传入纤维的活动介导的，而副交感神经介导的肠道传入神经支配主要与胃肠道疼痛的信号传递无关。至于肠道外周感觉受体的编码机制，有证据表明在某些位置（如胆道系统）存在特定的内脏伤害感受器，而在其他位置（如结肠）存在非特异性的“强度”型受体。无论如何，肠道中伤害性传入纤维的实际数量非常少，这就解释了为什么胃肠道的大片区域似乎不敏感，或者在产生疼痛感觉之前需要相当大的刺激。交感神经中含有的少数伤害性传入纤维可兴奋脊髓中的许多二级神经元，这些神经元继而在脊髓和脑干内产生广泛的发散，有时涉及长的脊髓上环路。这种发散性输入可激活许多不同的系统，包括运动、自主神经和感觉系统，并因此引发内脏伤害感受的典型一般反应：有时牵涉到躯体区域的弥漫性且定位不佳的疼痛，以及导致运动活动延长的自主神经和躯体反射。
