Department of Physiology and Pathophysiology, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi 710061, PR China.
Brain Res. 2010 Mar 31;1322:50-8. doi: 10.1016/j.brainres.2010.01.058. Epub 2010 Feb 1.
The aim of the present study was to investigate whether local application of octreotide, an analogue of somatostatin, suppresses the glutamate-evoked activities of Adelta and C primary afferent fibers innervating dorsal hairy skin of the rat in vivo. The single unit activity of Adelta and C afferent fibers was recorded in isolated filaments from the dorsal cutaneous branches of the T9-T12 spinal nerves. Changes in discharge relative to baseline during injection of glutamate (0.3mM, 10microL) into the receptive field with pretreatment by octreotide (20microM, 10microL) were compared with injection after pretreatment with normal saline. Most of Adelta fibers (21/27, 78%) and C fibers (21/26, 81%) in the dorsal cutaneous branches were significantly activated by local injection of glutamate following saline injection. The mean discharge rates increased from 2.39+/-0.30 and 2.42+/-0.37 impulses/min to 12.79+/-2.04 and 13.56+/-2.56 impulses/min during injection of glutamate for Adelta and C fibers, respectively. After octreotide pretreatment group, glutamate increased the mean discharge rates from 1.93+/-0.38 and 2.25+/-0.29 impulses/min to 6.11+/-0.9 and 6.31+/-1.18 impulses/min in Adelta fibers and C fibers, respectively. The discharge rates during injection of glutamate after octreotide pretreatment were significantly lower than after normal saline pretreatment. The suppressive effect of octreotide was reversed by the somatostatin receptor antagonist cyclo-somatostatin. These results suggest that interactions between excitatory amino acid and inhibitory neuropeptides may contribute to sensory signaling in the peripheral nervous system.
本研究旨在探讨局部应用奥曲肽(生长抑素类似物)是否抑制 somatostatin 类似物,抑制体内大鼠背毛皮肤感觉传入纤维中 Adelta 和 C 纤维的谷氨酸诱发活动。用 T9-T12 脊神经背皮支分离的单个纤维记录 Adelta 和 C 传入纤维的单位活动。在预先用奥曲肽(20μM,10μL)预处理后,将谷氨酸(0.3mM,10μL)注入感受野时,与预先用生理盐水预处理后相比,比较相对基线的放电变化。用生理盐水注射后,背皮支中的大多数 Adelta 纤维(21/27,78%)和 C 纤维(21/26,81%)被局部注射谷氨酸明显激活。Adelta 和 C 纤维的平均放电率分别从注射谷氨酸前的 2.39+/-0.30 和 2.42+/-0.37 脉冲/分钟增加到 12.79+/-2.04 和 13.56+/-2.56 脉冲/分钟。在奥曲肽预处理组中,谷氨酸使 Adelta 和 C 纤维的平均放电率分别从 1.93+/-0.38 和 2.25+/-0.29 脉冲/分钟增加到 6.11+/-0.9 和 6.31+/-1.18 脉冲/分钟。奥曲肽预处理后注射谷氨酸时的放电率明显低于生理盐水预处理后。奥曲肽的抑制作用可被 somatostatin 受体拮抗剂环 somatostatin 逆转。这些结果表明,兴奋性氨基酸和抑制性神经肽之间的相互作用可能有助于周围神经系统的感觉信号传递。