[1] Beaumont Hosp, Royal Coll Surg Ireland, Dept Clin Neurol Sci, Dublin 9, Ireland
[2] Univ Penn, Dept Pharmacol, Philadelphia, PA 19104 USA
[3] Univ Penn, Ctr Expt Therapeut, Philadelphia, PA 19104 USA
[4] Beaumont Hosp, Div Neurol, Dublin 9, Ireland