Regulation of nitric oxide synthase expression in motoneurons following nerve injury.
This study investigated the influence of postsynaptic targets and axonal ensheathing cells on the expression of nitric oxide synthase (NOS) in axotomized neurons. The hypoglossal and vagus nerves of adult rats were lesioned unilaterally, and axotomized neurons expressing NOS, identified by NADPH-diaphorase histochemistry and NOS immunocytochemistry, were counted as a function of time between 1 and 70 days postaxotomy. In the dorsal motor nucleus of the vagus (DMV), the number of NOS-positive neurons increased steadily with a time course which was not significantly different between the nerve crushed and transected groups. In the hypoglossal nucleus, each of four axotomy groups, namely, crushed, transected, ligated/transected, and avulsed, exhibited a distinct time course and extent of NOS expression, suggesting that postsynaptic targets and axonal ensheathing cells regulated NOS expression. The disparity between hypoglossal and DMV neurons in NOS expression may be due to the latters' unresponsiveness to, or inability to obtain the proper regulatory signals. Since cell loss was most severe in the hypoglossal nucleus following nerve avulsion, it appears that prolonged expression of NOS at high levels may be neurotoxic.
Yu
W H
WH
Department of Cell Biology and Anatomical Sciences, City University of New York Medical School, New York 10031, USA. ayu@scisun.sci.ccny.cuny.edu
D000818:Animals; D001369:Axons; D002452:Cell Count; D003714:Denervation; D008058:Dihydrolipoamide Dehydrogenase / Q000032:analysis; D004790:Enzyme Induction; D005260:Female; D007002:Hypoglossal Nerve / Q000201:enzymology / Q000502:physiology; D061228:Hypoglossal Nerve Injuries; D008026:Ligation; D009046:Motor Neurons / Q000201:enzymology*; D009409:Nerve Crush; D009416:Nerve Regeneration; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D012183:Retrograde Degeneration; D014630:Vagus Nerve / Q000201:enzymology / Q000502:physiology; D061223:Vagus Nerve Injuries
D009419:Nerve Tissue Proteins; D019001:Nitric Oxide Synthase; D008058:Dihydrolipoamide Dehydrogenase