tailieunhanh - Báo cáo khoa hoc:" Quantification of the effects of an alpha-2 adrenergic agonist on reflex properties in spinal cord injury using a system identification technique"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Quantification of the effects of an alpha-2 adrenergic agonist on reflex properties in spinal cord injury using a system identification technique | Mirbagheri et al. Journal of NeuroEngineering and Rehabilitation 2010 7 29 http content 7 1 29 J NER JOURNAL OF NEUROENGINEERING AND REHABILITATION RESEARCH Open Access Quantification of the effects of an alpha-2 adrenergic agonist on reflex properties in spinal cord injury using a system identification technique Mehdi M Mirbagheri 1 2 David Chen1 2 and W Zev Rymer1 2 Abstract Background Despite numerous investigations the impact of tizanidine an anti-spastic medication on changes in reflex and muscle mechanical properties in spasticity remains unclear. This study was designed to help us understand the mechanisms of action of tizanidine on spasticity in spinal cord injured subjects with incomplete injury by quantifying the effects of a single dose of tizanidine on ankle muscle intrinsic and reflex components. Methods A series of perturbations was applied to the spastic ankle joint of twenty-one spinal cord injured subjects and the resulting torques were recorded. A parallel-cascade system identification method was used to separate intrinsic and reflex torques and to identify the contribution of these components to dynamic ankle stiffness at different ankle positions while subjects remained relaxed. Results Following administration of a single oral dose of Tizanidine stretch evoked joint torque at the ankle decreased significantly p The peak-torque was reduced between 15 and 60 among the spinal cord injured subjects and the average reduction was 25 . Using systems identification techniques we found that this reduced torque could be attributed largely to a reduced reflex response without measurable change in the muscle contribution. Reflex stiffness decreased significantly across a range of joint angles p after using tizanidine. In contrast there were no significant changes in intrinsic muscle stiffness after the administration of tizanidine. Conclusions Our findings demonstrate that tizanidine acts to reduce reflex mechanical .