Lipski J, Kanjhan R, Kruszewska B, Smith M
Department of Physiology, School of Medicine, University of Auckland, New Zealand.
Neuroscience. 1995 Nov;69(2):601-18. doi: 10.1016/0306-4522(95)92652-z.
The aim of this study, conducted in anaesthetized rats, was to examine the morphology of barosensitive neurons in the rostral ventrolateral medulla and their immunoreactivity for a catecholamine synthesizing enzyme, tyrosine hydroxylase. Thirty neurons displaying inhibitory postsynaptic potentials following stimulation of the aortic depressor nerve were intracellularly labelled with Lucifer Yellow or Neurobiotin. Some of these neurons could be excited antidromically from the second thoracic segment of the spinal cord, with conduction velocities of spinal axons ranging from 1.9 to 7.2 m/s. The filled somas were found immediately caudal to the facial nucleus and ventral or ventromedial to compact formation of the nucleus ambiguus. Some dendrites reached the ventral medullary surface. Axons usually projected dorsomedially and then made a sharp rostral and/or caudal turn. The caudally projecting axon could, in some cases, be followed to the first cervical segment of the spinal cord. Seven cells issued fine axon collaterals on the ipsilateral side. These were identified mainly in two areas: in the rostral ventrolateral medulla (or immediately dorsomedial to that region), and within the dorsal vagal complex. Seven of 27 examined cells (26%) were tyrosine hydroxylase-immunoreactive and were classified as C1 adrenergic neurons. No clear relationship was found between the presence or absence of adrenergic phenotype and the morphology of filled cells. However, the amplitude of aortic nerve-evoked inhibitory postsynaptic potentials was significantly larger in tyrosine hydroxylase-positive neurons. Possible reasons for the low percentage of barosensitive cells with tyrosine hydroxylase immunoreactivity found in this study, in comparison with previously published estimates, are discussed. This is the first study describing the morphology of neurons in this part of the medulla identified as barosensitive in vivo, and directly demonstrating adrenergic phenotype in a subset of these neurons.
本研究在麻醉大鼠身上进行，目的是检查延髓头端腹外侧区压力感受性神经元的形态及其对儿茶酚胺合成酶酪氨酸羟化酶的免疫反应性。对30个在刺激主动脉减压神经后出现抑制性突触后电位的神经元，用路西法黄或神经生物素进行细胞内标记。其中一些神经元可被来自脊髓胸段的逆向兴奋，脊髓轴突的传导速度在1.9至7.2米/秒之间。被标记的胞体位于面神经核尾侧紧邻处，以及疑核致密部的腹侧或腹内侧。一些树突延伸至延髓腹侧表面。轴突通常向背内侧投射，然后急剧转向头端和/或尾端。在某些情况下，尾端投射的轴突可追踪至脊髓颈段。7个细胞在同侧发出细的轴突侧支，主要见于两个区域：延髓头端腹外侧区（或该区域紧邻的背内侧）以及迷走神经背核复合体内部。27个被检查细胞中有7个（26%）为酪氨酸羟化酶免疫反应阳性，被归类为C1肾上腺素能神经元。肾上腺素能表型的有无与被标记细胞的形态之间未发现明确关系。然而，酪氨酸羟化酶阳性神经元中，主动脉神经诱发的抑制性突触后电位的幅度显著更大。本文讨论了与先前发表的估计相比，本研究中酪氨酸羟化酶免疫反应阳性的压力感受性细胞比例较低的可能原因。这是第一项描述延髓这一部分在体内被确定为压力感受性的神经元形态，并直接证明其中一部分神经元具有肾上腺素能表型的研究。
