Kott J N, Vickland H, Dong X M, Westrum L E
Department of Neurological Surgery, University of Washington, Seattle 98195.
Exp Neurol. 1992 Jan;115(1):132-6. doi: 10.1016/0014-4886(92)90236-j.
Evidence suggests that tyrosine hydroxylase (TH) expression by juxtaglomerular (JG) neurons of the olfactory bulb (OB) is dependent upon input from primary olfactory neurons (ONs), which are identifiable using immunocytochemical localization (ICC-L) methods for olfactory marker protein (OMP). When the input from the continuously regenerating ONs is temporarily removed (either surgically or chemically), JG cells cease TH production until ON contact is reestablished. We are studying this transneuronal regulation using the rat OB in a transplantation (TX) model. Fetal OBs, labeled in utero with tritiated thymidine, were transplanted (TX) into a site vacated by removal of a neonatal host OB. Host animals were sacrificed at varying periods after TX. Alternate sets of frozen sections were then processed for autoradiography or using ICC-L for TH and OMP. As early as 1 week post-TX, OMP-positive fibers and glomerulus-like structures were seen throughout the TX OB. Despite this extensive and rapid OMP reinnervation, TH expression returned very slowly and the number of TH expressing cells never approached control levels. The reduced TH activity in TXs may be due to failure of JG cells to survive or to develop the correct phenotype under TX conditions. Alternatively, input from ON fibers may only be necessary, but not sufficient, for the expression of TH.
有证据表明，嗅球（OB）的球旁（JG）神经元中酪氨酸羟化酶（TH）的表达依赖于初级嗅觉神经元（ONs）的输入，而初级嗅觉神经元可通过嗅觉标记蛋白（OMP）的免疫细胞化学定位（ICC-L）方法来识别。当持续再生的ONs的输入被暂时去除（通过手术或化学方法）时，JG细胞停止产生TH，直到重新建立与ON的接触。我们正在使用大鼠OB的移植（TX）模型研究这种跨神经元调节。用氚标记胸腺嘧啶核苷在子宫内标记的胎儿OB被移植到通过切除新生宿主OB而腾出的部位。在TX后的不同时期处死宿主动物。然后对交替的冷冻切片进行放射自显影处理，或使用ICC-L检测TH和OMP。早在TX后1周，在移植的OB中就可见到OMP阳性纤维和肾小球样结构。尽管有这种广泛而迅速的OMP再支配，但TH表达恢复非常缓慢，且表达TH的细胞数量从未接近对照水平。TX中TH活性降低可能是由于JG细胞在TX条件下未能存活或未能发育出正确的表型。或者，ON纤维的输入对于TH的表达可能只是必要的，但并不充分。
