The endocannabinoid system is modulated in response to spinal cord injury in rats

Endocannabinoids are lipid mediators with protective effects in many diseases of the nervous system. We have studied the modulation of the endocannabinoid system after a spinal cord contusion in rats. In early stages, lesion induced increases of anandamide and palmitoylethanolamide (PEA) levels, an upregulation of the synthesizing enzyme NAPE-phospholipase D and a downregulation of the degradative enzyme FAAH. In delayed stages, lesion induced increases in 2-arachidonoylglycerol and a strong upregulation of the synthesizing enzyme DAGL-α, that is expressed by neurons, astrocytes and immune infiltrates. The degradative enzyme MAGL was also moderately increased but only 7 days after the lesion. We have studied the cellular targets for the newly formed endocannabinoids using RT-PCR and immunohistochemistry against CB1 and CB2 receptors. We observed that CB1 was constitutively expressed by neurons and oligodendrocytes and induced in reactive astrocytes. CB2 receptor was strongly upregulated after lesion, and mostly expressed by immune infiltrates and astrocytes. The endocannabinoid system may represent an interesting target for new therapeutical approaches to spinal cord injury.