Changes Of Neuronal Nitric Oxide Synthase Immunopositive Neurons In Brain Stem Of Diabetic Rats

Objective: To investigate the role of nitric oxide in diabetes mellitus and diabetic neuropathy in central nervous system by observing the changes of neuronal nitric oxide synthase (nNOS) immunopositive neurons in laterodorsal tegmental nucleus (LDT), subcoeruleus nucleus (SubC), dorsal central gray nucleus (DCG) and analyzing quantitatively with image analyzer in diabetic rats.Methods: 36 SD rats were divided randomly into control and diabetic groups. The diabetic group was first established STZ-induced diabetic rats, and then was sacrificed and the materials were drawn at the end of 2, 7 and 12 weeks. The number of nNOS immunopositive neurons in LDT, SubC and DCG was counted and analysed quantitatively by image analyzer. The changes of serum glucose and serum nitric oxide at every period were also analysed.Results: (1) The number of nNOS immunopositive neurons of LDT of the diabetic group in 2 weeks, 7 weeks and 12 weeks was significantly increased by comparison with that of the control group and kept relatively stable (P<0.01). The average optical density (AOD) and volum integrated optical density (VIOD) of the diabetic group in 2 weeks, 7 weeks and 12 weeks were more than that of the control group (P<0.01). (2) The number of nNOS immunopositive neurons of SubC of the diabetic group in 2 weeks, 7 weeks and 12 weeks was significantly increased (P<0.01), when compared with that of the control group. The AOD and VIOD of the diabetic group in course of the experiment were decreased slightly, however, significantly increased in comparison with that of the control group (P<0.01). (3) The number of nNOS immunopositive neurons of DCG of the diabetic group in 2 weeks, 7 weeks and 12 weeks was significantly increased when compared with that of the control group (P<0.01). The AOD and VIOD of diabetic group were significantly increased when performing an act of comparison with that of the control group (P<0.01). (4) The concentration of nitric oxide in serum of the diabetic group increased significantly in 2 weeks (P<0.01), then decreased to normal level from 7 weeks. Conclusions: (1) The number of nNOS immunopositive neurons and the content ofnNOS immunopositive substance in LDT, SubC and DCG were different from the content of nitric oxide in peripheral serum. It may be related to the lack of nitric oxide by catalysis of eNOS in peripheral serum. (2) The number of nNOS immunopositive neurons and the content of nNOS immunopositive substance in LDT, SubC and DCG were significantly increased. It suggested that the increased nitric oxide might be result in neurocyte toxic effect of nitric oxide that could destroy cellular architecture and function. (3) The number of nNOS immunopositive neurons and the content of nNOS immunopositive substance in LDT and SubC were significantly increased. It suggested that the increased nitric oxide might be related to sleep disorder that often occurred in diabetic late stage. (4) The number of nNOS immunopositive neurons and the content of nNOS immunopositive substance in DCG and SubC were significantly increased. It may be associated with sensory disturbance such as hyperesthesia and sensory deprivation in diabetic late stage.