Xuerong Zhang; Chaoqi Mu; Arabinda Mishra; Feng Wang; Pai-Feng Yang; Xinqiang Yan; Ming Lu; John C. Gore; Li Min Chen (2026).听.听Pain Reports, 11(2), e0000000000001368.听
This study used high-resolution functional MRI (fMRI), a technique that measures brain or spinal cord activity by detecting changes in blood flow (called the BOLD signal), to better understand how pain from heat is processed in the spinal cord. Specifically, the researchers focused on the lumbar (lower back) region of the spinal cord in rats. They applied a painful heat stimulus (47.5掳C) to one hind paw and recorded activity in spinal cord segments L3 to L5, while also collecting data during rest to examine how different regions communicate with each other.
The results showed that painful heat triggered increased activity in specific areas of the spinal cord鈥檚 gray matter, particularly in the聽dorsal horn聽(a region that processes sensory information like pain) and the聽intermediate zone聽(a region involved in integrating and relaying signals). These responses were strongest in segments L3 and L4, suggesting these areas play a key role in processing heat-related pain. Additionally, when the animals were at rest, the researchers found strong functional connectivity (synchronized activity) between similar regions on both sides of the spinal cord鈥攕pecifically between dorsal horns and between ventral horns (the latter being more involved in motor control)鈥攂ut not between different spinal segments. Based on these findings, the authors propose that a part of the L3 segment, known as the intermediate zone, may act as a central hub that helps regulate how pain signals are processed within the spinal cord.
Figure 1.:
High-resolution magnetization transfer contrast (MTC)-weighted anatomical images of the L3鈥揕5 spinal cord from a representative rat. (A) Left: schematic illustration of the research interest of lumbar spinal cord. Right: A typical axial slice of MTC image of lumbar spinal cord with the gray鈥搘hite matter boundary outlined by yellow lines. (B) Left: 5 axial MTC images acquired with slice 3 centered at the L3/L4 segment. Right: the corresponding axial slice positions overlaid on the coronal image in the middle line. (C) Schematics of 1 imaging session timeline and noxious heat stimulus presentation paradigm. D, dorsal; L, left; R, right; V, ventral.