- Studies on the influence of enriched-environment housing combined with systemic administration of an alpha2-adrenergic antagonist on spatial learning and hyperactivity after global ischemia in rats. Puurunen, K., Sirviö, J., Koistinaho, J., Miettinen, R., Haapalinna, A., Riekkinen, P., Sivenius, J. Stroke (1997)