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Dynamic variations of c‐ F os expression in the spinal cord exposed to intramuscular hypertonic saline‐induced muscle nociception
Author(s) -
Chen Y.K.,
Lei J.,
Jin L.,
Tan Y.X.,
You H.J.
Publication year - 2013
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1002/j.1532-2149.2012.00207.x
Subject(s) - saline , nociception , hypertonic saline , spinal cord , lumbar spinal cord , anesthesia , chemistry , endocrinology , lumbar , intraperitoneal injection , medicine , anatomy , receptor , psychiatry
Background Numerous studies focus on intramuscular (i.m.) injection of hypertonic saline‐induced muscle pain and nociception. The spatio‐temporal characteristics and dynamic variation of spinal neuronal activities elicited by i.m. hypertonic saline remain unknown. Methods The spatio‐temporal variations of c‐Fos expression in the lumbar spinal cord exposed to i.m. injection of 5.8% saline were investigated in male rats. Results After a unilateral i.m. 5.8% saline injection, c‐ F os expression in dorsal horn of spinal L4‐6 segments was significantly enhanced bilaterally ( p < 0.05 and p < 0.001). These 5.8% saline‐induced bilateral spinal Fos expression occurred rapidly 0.5 h following the i.m. injection, and reached the peak levels within 1 h, which declined gradually and returned to the control levels within 8 h. Compared with intact rats without i.m. insults, no significant influence of the spinalization on spinal c‐ F os expression was found. However, the 5.8% saline‐induced increases in F os expression in intact and spinalized rats differed significantly. During muscle nociception, the c‐ F os expression within the superficial layer (laminae I – II ) and the deep layer (laminae V – VI ) in spinalized rats were significantly lower and higher than that of in intact rats ( p < 0.05 and p < 0.001). Fentanyl (20 μg/kg, intraperitoneal) completely attenuated the 5.8% saline intramuscularly induced increases in c‐ F os expression in laminae III–VI ( p < 0.001), but not laminae I – II . Conclusions It is suggested that spinal nociceptive neuronal activities in superficial and deep layers may differently be modulated by endogenous descending facilitation and inhibition, respectively.