Analgesia induced by perineural clonidine is enhanced in persistent neuritis

Abstract

Alpha 2-adrenoceptors are concentrated near sites of peripheral nerve injury or inflammation, primarily on immune cells, and their activation reduces inflammation and hypersensitivity to tactile stimuli. These results were obtained during acute inflammation, but the efficacy of alpha2-adrenoceptor stimulation in persistent inflammation has not been tested. Here, we show that perineural injection of the alpha2-adrenoceptor agonist, clonidine, reduces hypersensitivity in persistent sciatic neuritis with an onset more rapid than acute neuritis. Perineural clonidine reduces microglial activation in the spinal cord in persistent, but not acute neuritis, and does not change the number of spinal neurons with phosphorylated transcription factor, cyclic adenosine monophosphate response element binding protein. These data support treatment strategies with alpha2-adrenoceptor agonists in persistent neuritis.