Knee　osteoarthritis　(KOA)　is　a　highly　prevalent,　chronic　joint　disorder,　which　can　lead　to　chronic　pain.　Although　electroacupuncture　(EA)　is　effective　in　relieving　chronic　pain　in　the　clinic,　the　involved　mechanisms　remain　unclear.　Reduced　diffuse　noxius　inhibitory　controls　(DNIC)　function　is　associated　with　chronic　pain　and　may　be　related　to　the　action　of　endocannabinoids.　In　the　present　study,　we　determined　whether　EA　may　potentiate　cannabinoid　receptor-mediated　descending　inhibitory　control　and　inhibit　chronic　pain　in　a　mouse　model　of　KOA.　We　found　that　the　optimized　parameters　of　EA　inhibiting　chronic　pain　were　the　low　frequency　and　high　intensity　(2　Hz　+　1　mA).　EA　reversed　the　reduced　expression　of　CB1　receptors　and　the　2-arachidonoylglycerol　(2-AG)　level　in　the　midbrain　in　chronic　pain.　Microinjection　of　the　CB1　receptor　antagonist　AM251　into　the　ventrolateral　periaqueductal　gray　(vlPAG)　can　reversed　the　EA　effect　on　pain　hypersensitivity　and　DNIC　function.　In　addition,　CB1　receptors　on　GABAergic　but　not　glutamatergic　neurons　are　involved　in　the　EA　effect　on　DNIC　function　and　descending　inhibitory　control　of　5-HT　in　the　medulla,　thus　inhibiting　chronic　pain.　Our　data　suggest　that　endocannabinoid　(2-AG)-CB1R-GABA-5-HT　may　be　a　novel　signaling　pathway　involved　in　the　effect　of　EA　improving　DNIC　function　and　inhibiting　chronic　pain.