VP.49 Total sleep deprivation leads to changes in neuromuscular junction of soleus muscle in male wistar rats

Abstract

Skeletal muscle atonia is a prominent feature of rapid eye movement sleep. Neuromuscular junction exhibits high morphological and functional plasticity. Sleep deprivation (SD) may influence NMJ morphology at presynaptic and postsynaptic terminals levels. In the present study, we have looked into the ultrastructural changes in the rat soleus muscle NMJ after sleep, sleep deprivation and recovery sleep. A total of 18 rats were divided into three groups. Group I rats had normal sleep wake cycle, group II rats were subjected to 24 h SD by running wheel method and group III rats had 24h recovery sleep. At the end of the study, soleus muscles were collected for electron microscopic and neurochemical study. Morphometry was performed and neurotransmitters were measured by ELISA. The study was conducted as per the guidelines of the Institutional Animal Ethics Committee (960/IAEC/16). Electron microscopic observation revealed a significant increase in mitochondrial density in 24h SD (p<0.01) as compared to control in presynaptic terminal. Further, in post synapse we found similar increase in SD (p<0.0002). Within group comparison of intact versus altered mitochondria exhibited a significant increase in the diameter of altered mitochondria in all the experimental groups (p≤0.0001). Moreover, within group comparison of area of intact versus altered mitochondria showed significant increase in area of altered mitochondria only in control (p= 0.01) and 24h SD (p= 0.02). Synaptic vesicle density we found to be significantly increased in 24h SD as compared to control (p=0.002), but not in recovery sleep at presynaptic terminal. Interestingly, the number of junctional folds per synapse profile was significantly increased in the 24h SD group as compared to control, (p= 0.002). Also, there was a significant difference between 24hr SD and recovery group (p= 0.002). Concentration of acetylcholine in 24 h sleep deprivation was decreased (p=0.02). In addition, but acetylcholine esterase activity was significantly increased (p= 0.02). The acetylcholine esterase activity did not come back to control level even after 24h of recovery sleep. Pearson correlation between acetylcholine and vesicular density showed found a negative correlation (r= 0.07, p<0.05) in 24h SD. These findings suggest that there are significant changes in neuromuscular junction of soleus muscle after24hr SD. We conclude that sleep plays a key role in NMJ homeostasis.