Establishment Of Rubrospinal Tract Lesion Model And Investigation Of The Protective Effects Of Estrogen On Axotomized Rubrospinal Neurons In Rats

Partâ… Localization of Rubrospinal Tract by Tracing Techniques in Spinal Cord in Adult RatsObjective: To detect the localization of rubrospinal tract (RST) in brain stem and spinal cord in adult rats. Methods: Anatomical localization of the rubrospinal tract were shown by using anterograde labeling with biotinylated dextran amine(BDA)and retrograde transport of Fluoro-Ruby (FR) in normal adult Sprague-Dawley rats. Results: The BDA labeled neurons located in the parvocellular and magnocellular portions of the red nucleus (RN) in midbrain. Then, the BDA labeled RST axons immediately decussate after leaving the red nucleus in the ventral tegmental decussation in the midbrain, and descend to the dorsal part of lateral funiculus, near the dorsal horn of the spinal cord. The FR retrograde transportation was located at the dorsal part of lateral funiculus in cervical segments and expressed in magnocellular red nucleus of midbrain. Conclusions: Using BDA anterograde labeling method and FR retrograde transport technique can reveal the anatomical localization of rubrospinal tract in rats and provide the morphological foundation for studying the lesion and functional recovery of rubrospinal tract. Partâ…¡Establishment and Assessment of Rubrospinal Tractotomy Model in Adult RatsObjective: To establish rubrospinal tract lesion model in adult rats successfully. Methods: Using forelimb spontaneous vertical exploration test, BDA anterograde tracing technique, Fluoro-Ruby retrograde transport technique and NADPH histochemistry were utilized to assess the function and morphology of rubrospinal tract lesion model. Results: Forelimbs extensors at left sides were paralyzed after unilateral rubrospinal tractotomy. Forelimbs spontaneous vertical exploration test showed the motor function of the lesion side were limited. BDA tracing method showed only one bundle of BDA positive fibers decussated from left to right descended to lumbar segments at the right part of dorsalateral funiculus of spinal cord. Under the level of injury, there was no BDA positive fibers descended in the left dorsalateral funiculus of spinal cord. FR tracing method showed that no significant differences were observed in number or mean soma size of neurons between the lesion side and the control side of RN at 4 weeks after surgery. But 8 weeks after injury, the number and mean soma size of neurons in the right RN were significantly decreased than those in control sides. NADPH histochemical staining showed that large number of NADPH positive cells and processes were seen in the lesion side of lateral funiculi of the spinal cord. Conclusions: These results indicated that red nucleus has been damaged retrogradely following the unilateral cervical rubrospinal tractotomy, which is an ideal animal model for studying the plasticity and regeneration of rubrospinal tract. BDA tracing technique and FR retrograde method are effective morphological assessments of rubrospinal tractotomy model. Part III Neuroprotective Effects of Estrogen on Rubrospinal Neuron following Spinal Cord Injury in Ovariectomized Sprague-Dawley RatObjective: To investigate the neuroprotective effects of estrogen on rubrospinal neurons and functional recovery following spinal cord injury in ovariectomized Sprague-Dawley Rat. Methods: Ovariectomized SD rats were divided into 5 groups: RST lesion group, E2 treatment group, ICI treatment group, E2+ICI treatment group and normal group. The RST funiculotomy models were made at the unilateral lateral funiculus at C3/C4 spinal cord. Forelimb spontaneous vertical exploration test, BDA anterograde tracing, FR retrograde tracing, NADPH histochemistry, GFAP fluorescent immunohistochemistry and immunoblot analysis were utilized to determine the neuroprotective effects of the estrogen on rubrospinal tract after rubrospinal tractotomy. Results: The amount of survival rubrospinal FR-labeled neurons in the area of RN in E2 treatment group was significantly higher than those in the controls. The expression levels of NOS and GFAP in the spinal cord and red nucleus were significantly decreased in E2 treated rats. Conclusions: These results indicate that estrogen may significantly reduce retrograde neural cell death and enhance functional recovery following SCI. Estrogen may play a neuroprotective role against spinal cord injury in the adult rat.