Silverman A J, Zimmerman E A
Neuroscience. 1982;7(11):2705-14. doi: 10.1016/0306-4522(82)90094-x.
The neurons of the paraventricular nucleus of the hypothalamus have a substantial vasopressin-containing projection to the zona externa of the median eminence. Several parameters of neuronal function are increased in these cells following adrenalectomy; these increases can be prevented by glucocorticoid treatment. We have now used this system to study the effect of adrenal removal on the sprouting of axons in response to a unilateral lesion of the paraventricular nucleus. Results obtained from both immunocytochemical and anterograde tracing experiments indicate that the capacity of the paraventricular nucleus axons to sprout is enhanced in adrenalectomized animals. Anterograde tracing experiments indicate that the projection from the paraventricular nucleus to the zona externa is predominately ipsilateral confirming the findings of Alonso & Assenmacher and that sprouting does not occur in intact animals with a unilateral paraventricular nucleus lesion. However, the zona externa of adrenalectomized animals with a unilateral paraventricular nucleus lesion is filled bilaterally with neurophysin terminals: the volume occupied by such fibers is the same as in non-lesioned, adrenalectomized animals. These findings are interpreted to indicate that sprouting can occur in this system if the animal is adrenalectomized. To estimate the time course of sprouting, animals were first adrenalectomized for 2 weeks and then a unilateral lesion placed in the paraventricular nucleus. Animals were killed 1-26 days following lesion placement and the brains processed for immunocytochemistry. Initial denervation in the zona externa due to the lesion can be detected by day 6 post-lesions while reinnervation (sprouting) is seen by day 26. The results suggest that the increase in metabolic activity induced by adrenalectomy in the vasopressin neurons under study may influence the ability of the axons of these cells to produce new terminals.
下丘脑室旁核的神经元有大量含血管加压素的投射纤维至正中隆起的外侧带。肾上腺切除术后，这些细胞的几个神经元功能参数会增加；糖皮质激素治疗可防止这些增加。我们现在利用这个系统来研究肾上腺切除对室旁核单侧损伤后轴突发芽的影响。免疫细胞化学和顺行追踪实验的结果表明，肾上腺切除的动物中室旁核轴突发芽的能力增强。顺行追踪实验表明，从室旁核到外侧带的投射主要是同侧的，这证实了阿隆索和阿森马赫的发现，并且在单侧室旁核损伤的完整动物中不会发生轴突发芽。然而，单侧室旁核损伤的肾上腺切除动物的外侧带两侧都充满了神经垂体素终末：这些纤维占据的体积与未损伤的肾上腺切除动物相同。这些发现被解释为表明，如果动物进行了肾上腺切除，这个系统中就会发生轴突发芽。为了估计轴突发芽的时间进程，首先将动物肾上腺切除2周，然后在室旁核放置单侧损伤。在损伤放置后1 - 26天处死动物，并对大脑进行免疫细胞化学处理。损伤后第6天可检测到外侧带因损伤导致的初始去神经支配，而在第26天可观察到再支配（轴突发芽）。结果表明，所研究的血管加压素神经元中肾上腺切除诱导的代谢活性增加可能会影响这些细胞轴突产生新终末的能力。
