Schneider Stephen P
Department of Physiology and Neuroscience Program, 2196 Biomedical Physical Sciences, Michigan State University, E. Lansing, MI 48824-3320, USA.
Brain Res. 2005 Feb 9;1034(1-2):71-89. doi: 10.1016/j.brainres.2004.11.046.
Relationships between neuronal firing pattern and mechanosensory input in the deep dorsal horn were investigated using whole-cell recordings from isolated hamster spinal cord with innervation from an attached skin patch. Neurons that fired repetitively to depolarizing current (tonic cells) responded to both moving and static stimulation of their cutaneous receptive fields, and discharged continuously for the duration of stimulus application. Neurons responding to depolarizing current with transient, rapidly adapting firing (phasic cells) were significantly more responsive to stimulus movement than to static skin contact. Phasic cells typically issued a brief discharge at the onset or termination of a stimulus; their responses during static skin contact were weaker than tonic cells. Tonic cells were activated during both ramp and steady-state skin indentations, whereas phasic cells responded with their strongest excitation to displacement velocities exceeding 8 microm/ms. Mechanosensory input to phasic cells originated primarily from low threshold receptors, whereas tonic cells demonstrated a mixture of inputs from both low and high threshold sources. A third class of neurons responded to depolarizing current with a pronounced firing delay and displayed a sensitivity to cutaneous stimuli that was similar to tonic cells except they showed a modest decrease in firing as skin indentation velocity increased. The results suggest a correlation between functional properties of mechanoreceptive afferent fibers and intrinsic discharge properties of laminae III-V neurons that may significantly influence integration of cutaneous mechanosensory information at the first spinal relay.
利用从带有附着皮肤片神经支配的分离仓鼠脊髓进行全细胞记录，研究了深背角神经元放电模式与机械感觉输入之间的关系。对去极化电流产生重复放电的神经元（紧张性细胞）对其皮肤感受野的移动和静态刺激均有反应，并在刺激施加期间持续放电。对去极化电流以短暂、快速适应放电做出反应的神经元（相位性细胞）对刺激移动的反应明显比对静态皮肤接触的反应更强。相位性细胞通常在刺激开始或结束时发出短暂放电；它们在静态皮肤接触期间的反应比紧张性细胞弱。紧张性细胞在斜坡和稳态皮肤压痕期间均被激活，而相位性细胞对超过8微米/毫秒的位移速度反应最强。相位性细胞的机械感觉输入主要来自低阈值感受器，而紧张性细胞则表现出来自低阈值和高阈值来源的混合输入。第三类神经元对去极化电流有明显的放电延迟反应，并且对皮肤刺激的敏感性与紧张性细胞相似，只是随着皮肤压痕速度增加它们的放电略有减少。结果表明，机械感受传入纤维的功能特性与脊髓板层III-V神经元的内在放电特性之间存在相关性，这可能会显著影响在脊髓第一级中继处皮肤机械感觉信息的整合。
