Ameliorated effects of high frequency sinusoidal vibration on c-fos expression of rat's spinal cord during tail suspension

Abstract

Objective To investigate whether high frequency sinusoidal vibration (HFV) influences c-fos immunoreactivity in the spinal cord after an exposure of simulated weightlessness and to study the mechanism of alteration in neuronal activity of the spindle cord in muscle spindle afferent pathways.Methods Thirty Sprague Dawley female rats were randomly assigned to 14-day tailsuspension group,14-day tail suspension plus HFV group and control group.Each group had 10 rats.Weightlessness was simulated by tail suspension of rats.The changes in the c-fos expression of spinal cord was detected by using immunohistochemistry technique. Results The results showed that c-fos immunoreactive neurons in control group were mainly concentrated in lamina Ⅳ-Ⅶ of the ipsilateral spinal cord.By 14 days of tail-suspension,both the total number of c-fos immunoreactive neurons and the pattern of their lamellar distribution showed significant change. The number of c-fos immunoreactive neurons in lamina Ⅳ,Ⅵ and Ⅶ and the total number of labeled neurons in lamina Ⅳ-Ⅶ were significantly increased when compared with those of control rats (P＜0.05).However,after 14-day tail-suspension plus HFV,the total number of c-fos immunoreactive neurons and the pattern of their lamellar distribution did not show substantial changes as compared with those of the control group (P＞0.05).The number of c-fos immunoreactive neurons in lamina Ⅳ,Ⅵ and Ⅶ and the total number of labeled neurons were significantly decreased when compared with those of tail-suspension rats (P＜0.05). Conclusions Our findings show that HFV plays an obvious resistant role against the increase of c fos expression of spinal cord under the condition of simulated weightlessness.It is suggested that the significant increase in neuronal excitation of the spinal cord in muscle spindle afferent pathways under the condition of simulated weightlessness is closely related to the decrease in the afferent message from muscle spindles. Key words: Weightlessness simulation; Spinal cord; Muscle spindles; Genes; Immunohistochemistry