Nitrone spin trapping compound N-tert-butyl-alpha-phenylnitrone prevents seizures induced by anticholinesterases

The neuroprotection afforded by spin trapping agents such as N-tert-butyl-a lpha-phenylnitrone (PBN) has lent support to the hypothesis that increased production of reactive oxygen species (ROS) is a major contributing factor to excitotoxicity, aging and cognitive decline. Little is known, however, a bout the pharmacological properties of PEN. We have compared the acute effe cts of PEN on the development of seizures induced by the irreversible acety lcholinesterase (AChE) inhibitor diisopropylphosphorofluoridate (DFP), the reversible AChE inhibitor physostigmine (PHY), the muscarinic cholinergic r eceptor agonist pilocarpine (PIL) and the glutamatergic receptor agonist ka inic acid (KA). Rats were sacrificed 90 min after the injection of seizure- inducing agents. In situ hybridization was used to detect the induction of immediate early gene (IEG) c-fos and c-jun mRNA's and the levels of AChE mR NA. The activity of AChE was visualized by AChE staining and quantified usi ng an in vitro AChE assay. The seizures correlated with the induction of IE G mRNA's with all agents used. The pre-treatment with 150 mg/kg of PEN prev ented DFP- and PHY-induced seizures and the related expression of IEG mRNA' s, but had no effect on PIL or KA-induced seizures and associated IEG mRNA' s changes. PBN prevented seizures and significantly protected AChE activity against DFP inhibition when given before, but not when given after DFP. Th is study shows that PBN specifically protects against anticholinesterase-in duced seizures by reversible protection of AChE activity and not by the blo ckade of muscarinic or glutamate receptors, reactivation of AChE or scaveng ing of ROS. The anticholinesterase properties should be considered when usi ng PBN in studies of cholinergic dysfunction. (C) 1999 Elsevier Science B.V . All rights reserved.