Bice T N, Beal J A
Department of Cellular Biology and Anatomy, Louisiana State University Medical Center in Shreveport, 71130, USA.
J Comp Neurol. 1997 Dec 1;388(4):565-74. doi: 10.1002/(sici)1096-9861(19971201)388:4<565::aid-cne5>3.0.co;2-0.
Dual retrograde axonal tracers, Fluoro-Gold (FG) and true blue (TB), were used in conjunction with [3H]thymidine autoradiography to determine the number and neurogenic pattern of neurons with supraspinal projections in the superficial dorsal horn (SDH), i.e., laminae I and II, in spinal segment L1 of the rat. FG was injected into rostral brain centers (dorsal thalamus and midbrain), and TB was injected into the caudal brainstem (medulla) in young adult rats previously administered [3H]thymidine in utero. Following stereological correction, each dorsal horn had an average of 1.22 neurons in lamina I and 0.24 neurons in lamina II that had supraspinal projections per 10-microm transverse section. In the SDH, 52% of the neurons with supraspinal projections were found to project to rostral brain centers alone, 3.0% only to the caudal brainstem, and 45% to both areas. There was no significant difference in the percentage distribution of each of the three groups of neurons between lamina I and lamina II. Cell counts in the present study, in conjunction with previous observations in the literature, suggest that the majority of supraspinal projection neurons in the SDH fall into two groups: 1) spinomesencephalic neurons with collaterals to the medulla and 2) spinothalamic neurons with collaterals to the midbrain. The neurogenesis of supraspinal projection neurons in the SDH proceeded along an axon-length gradient, whereby neurons with the longest axons, those with projections to rostral brain centers, completed neurogenesis prior to neurons with shorter axons, those with projections only to the caudal brainstem. The generation of all SDH neurons with supraspinal projections was completed on embryonic day 14 (E14), 2 days prior to the completion of neurogenesis for SDH neurons with intraspinal projections.
双逆行轴突示踪剂氟金（FG）和真蓝（TB）与[3H]胸腺嘧啶核苷放射自显影术联合使用，以确定大鼠L1脊髓节段浅表背角（SDH）即I层和II层中具有脊髓上投射的神经元的数量和神经发生模式。在成年幼鼠子宫内预先给予[3H]胸腺嘧啶核苷后，将FG注入脑前部中枢（背侧丘脑和中脑），将TB注入脑后部脑干（延髓）。经过体视学校正后，每10微米横切面中，每个背角I层平均有1.22个具有脊髓上投射的神经元，II层有0.24个。在SDH中，发现52%具有脊髓上投射的神经元仅投射到脑前部中枢，3.0%仅投射到脑后部脑干，45%投射到两个区域。I层和II层之间这三组神经元的百分比分布没有显著差异。本研究中的细胞计数与文献中先前的观察结果表明，SDH中大多数脊髓上投射神经元可分为两组：1）具有至延髓侧支的脊髓中脑神经元和2）具有至中脑侧支的脊髓丘脑神经元。SDH中脊髓上投射神经元的神经发生沿轴突长度梯度进行，即轴突最长的神经元（那些投射到脑前部中枢的神经元）在轴突较短的神经元（那些仅投射到脑后部脑干的神经元）之前完成神经发生。所有具有脊髓上投射的SDH神经元的生成在胚胎第14天（E14）完成，比具有脊髓内投射的SDH神经元神经发生完成提前2天。
