Starbuck Elizabeth M, Wilson Wendy L, Fitts Douglas A
Department of Psychology, University of Washington, Box 351525, Seattle 98195-1525, USA.
Brain Res. 2002 Mar 29;931(2):159-67. doi: 10.1016/s0006-8993(02)02273-4.
If receptors in the gut relay information about increases in local osmolality to the brain via the vagus nerve, then vagotomy should diminish this signaling and reduce both thirst and brain Fos-like immunoreactivity (Fos-ir). Water intake in response to hypertonic saline (i.p. or i.g., 1 M NaCl, 1% BW; i.g., 0.6 M NaCl, 0.5% BW) was reduced during 120 min in rats with subdiaphragmatic vagotomy (VGX) compared to sham-VGX rats. Brain Fos-ir was examined in response to both i.g. loads. After the smaller load, VGX greatly reduced Fos-ir in the supraoptic nucleus (SON) and the magnocellular and parvocellular areas of the paraventricular nucleus (PVN). Fos-ir in the subfornical organ (SFO) and nucleus of the solitary tract (NTS) was not affected. After the larger load, VGX significantly reduced Fos-ir in the parvocellular PVN and in the NTS, but not in the other regions. Thus, decreased water intake by VGX rats was accompanied by decreased Fos-ir in the parvocellular PVN after the same treatments, indicating a role for the abdominal vagus in thirst in response to signaling from gut osmoreceptors. The decreased water intake in the VGX group was not reflected as a decrease in Fos-ir in the SFO. Absorption of the larger i.g. load may have activated Fos-ir through more rapidly increasing systemic osmolality, thereby obscuring a role for the vagus at this dose in the SON and magnocellular PVN.
如果肠道中的感受器通过迷走神经将局部渗透压升高的信息传递给大脑，那么迷走神经切断术应该会减弱这种信号传递，并减少口渴感和大脑中Fos样免疫反应性（Fos-ir）。与假手术组大鼠相比，膈下迷走神经切断术（VGX）大鼠在120分钟内对腹腔注射或灌胃高渗盐水（腹腔注射或灌胃，1M NaCl，1%体重；灌胃，0.6M NaCl，0.5%体重）的水摄入量减少。研究了灌胃负荷后大脑中的Fos-ir。在较小负荷后，VGX大大降低了视上核（SON）以及室旁核（PVN）的大细胞和小细胞区域的Fos-ir。穹窿下器官（SFO）和孤束核（NTS）中的Fos-ir不受影响。在较大负荷后，VGX显著降低了PVN小细胞区域和NTS中的Fos-ir，但在其他区域没有降低。因此，VGX大鼠水摄入量的减少伴随着相同处理后PVN小细胞区域Fos-ir的减少，表明腹部迷走神经在响应肠道渗透压感受器信号时对口渴感起作用。VGX组水摄入量的减少并未表现为SFO中Fos-ir的减少。较大灌胃负荷的吸收可能通过更快地增加全身渗透压激活了Fos-ir，从而掩盖了该剂量下迷走神经在SON和PVN大细胞区域中的作用。
