Clough R W, Peterson B R, Steenbergen J L, Jobe P C, Eells J B, Browning R A, Mishra P K
Department of Anatomy, Southern Illinois University School of Medicine-Carbondale, 62901-6523, USA.
Epilepsy Res. 1998 Jan;29(2):135-46. doi: 10.1016/s0920-1211(97)00076-4.
A primary determinant of seizure susceptibility and severity in genetically epilepsy-prone rats (GEPRs), is a generalized deficiency in the central noradrenergic system of these animals. In particular, this deficiency includes reduced numbers of norepinephrine (NE) synaptic terminals in several brain areas and distinctly fewer NE axons within the auditory tectum. Two strains of GEPRs have been developed: GEPR-3s that have moderately severe clonic seizures and GEPR-9s that have severe tonic seizures culminating in complete hindlimb extension. Seizures in animals of each substrain are preceded by a brief episode of wild running. The developmental profile of NE axonal growth in GEPRs compared to control rats is not known, but may be causally related to NE deficiencies in this seizure model. The present study compared developmental neurite extension of fetal NE neurons in vitro between GEPR-3s and Sprague-Dawley control rats, the strain from which GEPR-3s were originally derived. Neurite arborization of individual NE neurons was assessed by quantitative morphometry following immunocytochemical identification of tyrosine hydroxylase (TH). Preliminary studies using explant and dispersed-cell cultures of control-rat tissues showed that optimal culture parameters to support neuritogenesis of LC neurons included the use of dispersed-cell cultures, Pronectin-F substrate, day-14 gestation donor-tissue, no use of cytosine-arabinofuranoside (ARA-c, a glial mitotic inhibitor) and the presence of co-cultured tectal tissue. Compared to fetal control-rat NE neurons co-cultured with fetal control-rat tectum, NE neurons derived from fetal GEPR-3 LC in co-culture with GEPR-3 tectum exhibited only 30% of the neurite extension of control-rat LC neurons and GEPR-3 LC neurons had a similarly deficient amount of branching. This study suggests, but does not prove, that deficiency in tectal NE in GEPR-3s involves a developmental deficiency in neurite extension from GEPR-3 LC neurons. Hypothetically, this deficiency may also contribute to the well described NE deficiency in other regions of the adult GEPR brain.
在遗传性癫痫易感大鼠（GEPRs）中，癫痫易感性和严重程度的一个主要决定因素是这些动物中枢去甲肾上腺素能系统的普遍缺陷。具体而言，这种缺陷包括几个脑区中去甲肾上腺素（NE）突触终末数量减少，以及听觉顶盖内的NE轴突明显减少。已培育出两种GEPRs品系：发作程度为中度严重阵挛性发作的GEPR-3s和发作程度为严重强直性发作并最终导致后肢完全伸展的GEPR-9s。每个亚系动物的癫痫发作之前都有一段短暂的疯狂奔跑期。与对照大鼠相比，GEPRs中NE轴突生长的发育情况尚不清楚，但可能与该癫痫模型中的NE缺陷存在因果关系。本研究比较了GEPR-3s和Sprague-Dawley对照大鼠（GEPR-3s最初源自该品系）胎儿NE神经元在体外的发育性神经突延伸情况。在通过免疫细胞化学鉴定酪氨酸羟化酶（TH）后，采用定量形态学方法评估单个NE神经元的神经突分支情况。使用对照大鼠组织的外植体和分散细胞培养的初步研究表明，支持LC神经元神经突生成的最佳培养参数包括使用分散细胞培养、纤连蛋白-F底物、妊娠第14天的供体组织、不使用阿糖胞苷（ARA-c，一种胶质细胞有丝分裂抑制剂）以及存在共培养的顶盖组织。与与对照大鼠胎儿顶盖共培养的对照大鼠胎儿NE神经元相比，与GEPR-3顶盖共培养的源自GEPR-3 LC胎儿的NE神经元的神经突延伸仅为对照大鼠LC神经元的30%，且GEPR-3 LC神经元的分支数量同样不足。本研究表明，但未证明，GEPR-3s顶盖NE缺陷涉及GEPR-3 LC神经元神经突延伸的发育缺陷。假设这种缺陷也可能导致成年GEPR大脑其他区域中已被充分描述的NE缺陷。
