Zanzinger J, Czachurski J, Offner B, Seller H
I. Physiologisches Institut, Universität Heidelberg, Germany.
Brain Res. 1994 Sep 12;656(2):353-8. doi: 10.1016/0006-8993(94)91479-6.
Tonic sympathetic activity in vivo is continuously modulated by inhibitory and excitatory reflex mechanisms. We studied the properties of somato-sympathetic excitatory reflex transmission in the rostral ventrolateral medulla (RVLM) of baroreceptor-denervated and vagotomized chloralose-anesthetized cats. Electrical stimulation of the left intercostal nerve of the 4th thoracic segment (IC-T4) elicited an early spinal and a late supraspinal reflex in the ipsilateral white ramus T3 from which recordings were made. Bilateral cooling of the ventral surface of the RVLM reversibly reduced the supraspinal reflex amplitude to 18.0 +/- 3.1% of control (100%). The spinally evoked reflex was enhanced to maximally 154.7 +/- 5.3%. Cooling of only the ipsilateral side of the RVLM was nearly equieffective in both, suppressing the supraspinal and enhancing the spinal reflex component. In contrast, cooling of the contralateral side had no significant effects on supraspinal reflex transmission but caused slight increases of the spinal reflex amplitudes. Similar effects were obtained by microinjection (RVLM) of the glutamate antagonist kynurenic acid (5 x 10(-3) M, n = 7) and the specific non-NMDA receptor antagonist CNQX (4 x 10(-3) M, n = 4) which, however, blocked the supraspinal reflex less effectively. These results demonstrate that the RVLM represents an essential relay in the transmission of both somatosympathetic reflex components. The experiments further suggest an almost completely ipsilateral neuronal pathway for the supraspinal reflex component which projects from the RVLM to the intermediolateral cell column (IML). The descending inhibition of the spinal reflex, however, receives neuronal inputs from the contralateral side.
体内的交感神经紧张性活动不断受到抑制性和兴奋性反射机制的调节。我们研究了在去压力感受器神经支配和迷走神经切断的氯醛糖麻醉猫的延髓头端腹外侧区（RVLM）中躯体交感神经兴奋性反射传递的特性。电刺激第4胸段的左肋间神经（IC-T4）在同侧T3白交通支诱发早期脊髓反射和晚期脊髓上反射，并进行记录。RVLM腹侧面的双侧冷却可使脊髓上反射幅度可逆性降低至对照值（100%）的18.0±3.1%。脊髓诱发反射增强至最大154.7±5.3%。仅冷却RVLM的同侧在抑制脊髓上反射和增强脊髓反射成分方面几乎具有同等效果。相反，冷却对侧对脊髓上反射传递无显著影响，但导致脊髓反射幅度略有增加。通过向RVLM微量注射谷氨酸拮抗剂犬尿氨酸（5×10⁻³ M，n = 7）和特异性非NMDA受体拮抗剂CNQX（4×10⁻³ M，n = 4）也获得了类似的效果，然而，它们对脊髓上反射的阻断效果较差。这些结果表明，RVLM是躯体交感神经反射两个成分传递中的一个重要中继站。实验进一步提示，脊髓上反射成分存在几乎完全同侧的神经元通路，从RVLM投射到中间外侧细胞柱（IML）。然而，脊髓反射的下行抑制接受来自对侧的神经元输入。
