Abstract: Objective To observe the effects of melatonin on synaptic plasticity impaired by spinal cord injury in rats. Methods A total of 54 female Sprague-Dawley rats were divided into sham group (n=18), control group (n=18) and melatonin group (n=18). Spinal cord injury model was established with modified Allen's method at T10 (10 g from 25 mm height). The number of neurons and the expression of the Nissl body were detected with immunofluorescence and Nissl staining. The expression of neurofilament-200 (NF-200), brain-derived neurotrophic factors (BDNF), Synapsin I and growth-associated protein-43 (GAP-43) was detected with Western blotting. Results Seven days after injury, the number of motoneurons, the expression of Nissl body in motoneurons, and the expression of BDNF, Synapsin I and GAP-43 decreased in the control group compared with those in the sham group, and they increased in the melatonin group compared with those in the control group. Conclusion Melatonin can repair the impaired synaptic plasticity, which might promote the functional recovery after spinal cord injury.

Key words: spinal cord injury, synaptic plasticity, melatonin, rats