Finger T E, Böttger B
Department of Cellular and Structural Biology, University of Colorado School of Medicine, Denver 80262.
Neurosci Lett. 1992 Aug 31;143(1-2):15-8. doi: 10.1016/0304-3940(92)90222-s.
In the olfactory bulb, expression of tyrosine hydroxylase (TH) in juxtaglomerular neurons is dependent on innervation by the olfactory nerve. The presence of the neuropeptide calcitonin gene-related peptide (CGRP) within the olfactory nerve has led to the hypothesis that CGRP is responsible for regulation of TH expression in the bulbar neurons. On the other hand, other investigators claim that olfactory receptors never produce CGRP and that functional contact with olfactory axons regulates production of TH by bulbar neurons. Two different experimental procedures were used to test whether either CGRP or contact with the olfactory nerve is essential for production of TH by bulbar neurons in vivo. The peptidergic innervation of the olfactory bulb was eliminated either by neonatal capsaicin treatment, or by stereotaxic, electrolytic lesions of the ophthalmic division of the trigeminal nerve. Both of the treatments leave the olfactory innervation of the bulb intact while eliminating the CGRP-immunoreactive fibers in the olfactory nerve and glomeruli. Subsequent immunocytochemistry reveals a normal complement of bulbar TH-immunoreactive juxtaglomerular neurons in the absence of peptidergic innervation. In order to test whether olfactory nerve input is necessary for expression of TH in vivo, the anlage of the olfactory bulb was removed from embryonic (E16) rat pups and transplanted into the anterior chamber. These ectopic olfactory bulbs, although devoid of olfactory nerve input, contain numerous TH-immunoreactive neurons. Thus olfactory nerve input is not necessary for expression of TH in bulbar neurons.
在嗅球中，酪氨酸羟化酶（TH）在近球神经元中的表达依赖于嗅神经的支配。嗅神经中存在神经肽降钙素基因相关肽（CGRP），这引发了一种假说，即CGRP负责调节球部神经元中TH的表达。另一方面，其他研究人员声称，嗅觉受体从不产生CGRP，并且与嗅轴突的功能性接触调节球部神经元中TH的产生。使用两种不同的实验方法来测试CGRP或与嗅神经的接触对于球部神经元在体内产生TH是否必不可少。通过新生期辣椒素处理或通过立体定向电解损伤三叉神经眼支来消除嗅球的肽能神经支配。两种处理均使嗅球的嗅觉神经支配保持完整，同时消除嗅神经和肾小球中CGRP免疫反应性纤维。随后的免疫细胞化学显示，在没有肽能神经支配的情况下，球部TH免疫反应性近球神经元的数量正常。为了测试嗅神经输入对于体内TH表达是否必要，将嗅球原基从胚胎（E16）大鼠幼崽中取出并移植到前房中。这些异位嗅球虽然没有嗅神经输入，但含有大量TH免疫反应性神经元。因此，嗅神经输入对于球部神经元中TH的表达不是必需的。
