It is well known that overload changes the mechanical properties of biological tissues and fasting changes the responsiveness of intestinal afferents. This study aimed to characterize the effect of overload on mechanosensitivity in mesenteric afferent nerves in normal and fasted Sprague–Dawley rats. Food was restricted for 7 days in the Fasting group. Jejunal whole afferent nerve firing was recorded during three distensions, i.e., ramp distension to 80 cmH₂O luminal pressure (D1), sustained distension to 120 cmH₂O for 2 min (D2), and again to 80 cmH₂O (D3). Multiunit afferent recordings were separated into low-threshold (LT) and wide-dynamic-range (WDR) single-unit activity for D1 and D3. Intestinal deformation (strain), distension load (stress), and firing frequency of mesenteric afferent nerve bundles [spike rate increase ratio (SRIR)] were compared at 20 cmH₂O and 40 cmH₂O and maximum pressure levels among distensions and groups. SRIR and stress changes showed the same pattern in all distensions. The SRIR and stress were larger in the Fasting group compared to the Control group (P < 0.01). SRIR was lower in D3 compared to D1 in controls (P < 0.05) and fasting rats (P < 0.01). Total single units and LT were significantly lower in Fasting group than in Controls at D3. LT was significantly higher in D3 than in D1 in Controls. Furthermore, correlation was found between SRIR with stress (R = 0.653, P < 0.001). In conclusion, overload decreased afferent mechanosensitivity in a stress-dependent way and was most pronounced in fasting rats. Fasting shifts LT to WDR and high pressure shifts WDR to LT in response to mechanical stimulation.

众所周知，超负荷改变了生物组织的机械性能，而禁食改变了肠道传入的反应性。这项研究旨在表征超负荷对正常和禁食的Sprague-Dawley大鼠肠系膜传入神经机械敏感性的影响。在禁食组中禁食7天。在三种扩张期间记录空肠全传入神经放电，即斜向扩张至80 cmH ₂ O腔压力（D1），持续扩张至120 cmH ₂ O 2分钟（D2）和再次扩张至80 cmH ₂O（D3）。D1和D3的多单位传入记录被分为低阈值（LT）和宽动态范围（WDR）单个单元活动。比较了20 cmH ₂ O和40 cmH ₂ O的肠系膜传入神经束的肠变形（应变），扩张负荷（应力）和击发频率[峰值速率增加率（SRIR）]以及扩张和组间的最大压力水平。SRIR和压力变化在所有扩张中均显示出相同的模式。与对照组相比，空腹组的SRIR和压力更大（P  <0.01）。与对照组（P  <0.05）和空腹大鼠（P <0.05 <0.01）。空腹组的总单个单位和LT显着低于对照组，在第3天。D3组的LT显着高于对照组的D1组。此外，还发现SRIR与应力之间存在相关性（R  = 0.653，P  <0.001）。总之，超负荷以应力依赖的方式降低传入机械敏感性，在空腹大鼠中最为明显。禁食将LT转换为WDR，而高压将WDR转换为LT，以响应机械刺激。