Chemical Sympathectomy, but not Adrenergic Blockade, Improves Stroke Outcome

Background: A robust adrenergic response following stroke impairs lymphocyte function, which may prevent the development of autoimmune responses to brain antigens. We tested whether inhibition of the sympathetic response after stroke would increase the propensity for developing autoimmune responses to brain antigens. Methods: Male Lewis rats were treated with 6-hydroxydopamine (OHDA) prior to middle cerebral artery occlusion (MCAO), labetalol after MCAO, or appropriate controls. Behavior was assessed weekly and animals survived to 1 month at which time ELISPOT assays were done on lymphocytes from spleen and brain to determine the TH1 and TH17 responses to myelin basic protein (MBP), ovalbumin (OVA), and concanavalin A. A subset of animals was sacrificed 72 hours after MCAO for evaluation of infarct volume and lymphocyte responsiveness. Plasma C-reactive protein (CRP) was measured as a biomarker of systemic inflammation. Results: Despite similar initial stroke severity and infarct volumes, 6-OHDA-treated animals lost less weight and experienced less hyperthermia after stroke. 6-OHDA-treated animals also had decreased CRP in circulation early after stroke and experienced better neurological outcomes at 1 month. The TH1 and TH17 responses to MBP did not differ among treatment groups at 1 month, but the TH1 response to OVA in spleen was more robust in labetalol and less robust in 6-OHDA-treated animals. Conclusions: Chemical sympathectomy with 6-OHDA, but not treatment with labetalol, decreased systemic markers of inflammation early after stroke and improved long-term outcome. An increase in TH1 and TH17 responses to MBP was not seen with inhibition of the sympathetic response.