Gastrointestinal Diseases Research Unit, Queen's University, 76 Stuart Street, Kingston, ON, K7L 2V7, Canada.
Department of Physiology, Jordan University of Science and Technology, Irbid, Jordan.
Cell Tissue Res. 2023 Jun;392(3):659-670. doi: 10.1007/s00441-023-03769-3. Epub 2023 Apr 1.
The gut-brain axis has received increasing attention recently due to evidence that colonic microbes can affect brain function and behavior. However, little is known about the innervation of the colon by a major component of the gut-brain axis, vagal afferent neurons. Furthermore, it is currently unknown whether individual NG neurons or DRG neurons innervate both the proximal and distal colon. We aimed to quantify the number of vagal and spinal afferent neurons that innervate the colon; and determine whether these individual neurons simultaneously innervate the mouse proximal and distal colon. C57Bl/6 mice received injections of a combination of retrograde tracers that were either injected into the muscularis externa of the proximal or the distal colon: fast blue, DiI and DiO. Five to seven percent of lumbosacral and thoracolumbar spinal afferent neurons, and 25% of vagal afferent neurons were labelled by injections of DiI and DiO into the colon. We also found that approximately 8% of NG neurons innervate the distal colon. Ten percent of labeled thoracolumbar and 15% of labeled lumbosacral DRG neurons innervate both the distal and proximal colon. Eighteen percent of labeled NG neurons innervated both the distal and proximal colon. In conclusion, vagal afferent innervation of the distal colon is less extensive than the proximal colon, whereas a similar gradient was not observed for the spinal afferent innervation. Furthermore, overlap appears to exist between the receptive fields of vagal and spinal afferent neurons that innervate the proximal and distal colon.
肠脑轴最近受到了越来越多的关注，因为有证据表明结肠微生物可以影响大脑功能和行为。然而，对于肠脑轴的一个主要组成部分——迷走传入神经元对结肠的支配，人们知之甚少。此外，目前尚不清楚单个 NG 神经元或 DRG 神经元是否同时支配近端和远端结肠。我们的目的是量化支配结肠的迷走和脊髓传入神经元的数量；并确定这些单个神经元是否同时支配小鼠的近端和远端结肠。C57Bl/6 小鼠接受了逆行示踪剂的组合注射，这些示踪剂分别注射到近端或远端结肠的外肌层：快蓝、DiI 和 DiO。5%到 7%的腰骶和胸腰脊髓传入神经元，以及 25%的迷走传入神经元通过将 DiI 和 DiO 注射到结肠而被标记。我们还发现，大约 8%的 NG 神经元支配远端结肠。10%的标记胸腰 DRG 神经元和 15%的标记腰骶 DRG 神经元支配远端和近端结肠。18%的标记 NG 神经元支配远端和近端结肠。总之，迷走传入神经对远端结肠的支配不如近端结肠广泛，而脊髓传入神经的支配则没有观察到类似的梯度。此外，支配近端和远端结肠的迷走和脊髓传入神经元的感受野似乎存在重叠。
