Vizzard M A, Erdman S L, de Groat W C
University of Pittsburgh, School of Medicine, Department of Pharmacology, PA 15261, USA.
Neuroscience. 1995 Jul;67(1):1-5. doi: 10.1016/0306-4522(95)00137-8.
Nitric oxide synthase which is constitutively expressed in some neurons can be induced in other neurons by pathological conditions. For example, sciatic nerve or pelvic nerve transection induced nitric oxide synthase expression in lumbosacral dorsal root ganglion cells. This occurred in small to medium sized dorsal root ganglion neurons suggesting that this change might be limited to, or most prominent in, C-fiber afferents. These afferents are also very sensitive to the neurotoxin, capsaicin, which can deplete neuropeptide stores in C-fibers and in high doses cause degeneration of C-fiber afferent pathways. The present study was undertaken to determine if a chemically induced injury elicited in small diameter afferent neurons by systemic administration of capsaicin can induce a change in nitric oxide synthase expression similar to that elicited by peripheral nerve injury. Following capsaicin pretreatment (three days) a significant increase in the number of nitric oxide synthase-immunoreactive cells was detected in dorsal root ganglia. The increase was most prominent (34-63 fold) in the L5-S1 dorsal root ganglia but also substantial (2-17 fold) in cervical, caudal thoracic and rostral lumbar dorsal root ganglia. These results indicate that the expression of nitric oxide synthase-immunoreactivity in afferent neurons in the dorsal root ganglia is plastic and can be upregulated in response to chemical stimulation and/or injury. It is possible that nitric oxide formed by enhanced expression of nitric oxide synthase may play a role in capsaicin-induced neurotoxicity.
一氧化氮合酶在一些神经元中组成性表达，在其他神经元中可由病理状况诱导产生。例如，坐骨神经或盆腔神经横断可诱导腰骶部背根神经节细胞中一氧化氮合酶的表达。这种情况发生在中小型背根神经节神经元中，提示这种变化可能局限于C纤维传入神经，或在其中最为显著。这些传入神经对神经毒素辣椒素也非常敏感，辣椒素可耗尽C纤维中的神经肽储备，高剂量时可导致C纤维传入通路退变。本研究旨在确定通过全身给予辣椒素在小直径传入神经元中引发的化学性损伤是否能诱导一氧化氮合酶表达的变化，类似于外周神经损伤所引发的变化。在辣椒素预处理（三天）后，在背根神经节中检测到一氧化氮合酶免疫反应性细胞数量显著增加。这种增加在L5 - S1背根神经节中最为显著（34 - 63倍），但在颈、尾胸和腰上部背根神经节中也很可观（2 - 17倍）。这些结果表明，背根神经节传入神经元中一氧化氮合酶免疫反应性的表达具有可塑性，可因化学刺激和/或损伤而上调。一氧化氮合酶表达增强所形成的一氧化氮可能在辣椒素诱导的神经毒性中起作用。
