Comparison of neuroprotective effects induced by alpha-phenyl-N-tert-butyl nitrone (PBN) and N-tert-butyl-alpha-(2 sulfophenyl) nitrone (S-PBN) in lithium-pilocarpine status epilepticus

Abstract

The status epilepticus (SE) induced in rats by lithium-pilocarpine (Li-pilo) shares many common features with soman-induced SE including extensive limbic neuropathology. Reactive oxygen species are hypothesized to play a role in the SE induced neuropathology and we propose that the free radical scavengers alpha-phenyl-N-tert-butyl nitrone (PBN) and N-tert-butyl-alpha-(2 sulfophenyl) nitrone (S-PBN) may be neuroprotective. PBN or S-PBN were administered either immediately following pilocarpine (exposure treatment) or 5 min after the onset of SE as determined by ECoG activity. SE was allowed to continue for 3 h before termination with propofol. The rats were sacrified 24 h following pilocarpine administration. S-PBN induced minor effects to reduce SE duration and improve neurological deficit 24 h following pilocarpine administration. One hundred and fifty milligrams per kilograms PBN administered 5 min after SE onset produced significant neuroprotection in the parietal, occipital, perirhinal and piriform cortices as well as the lateral amygdala. One hundred and fifty milligrams per kilograms S-PBN was neuroprotective only in the occipital and perirhinal cortex while 300 mg/kg S-PBN exacerbated cortical neuropathology. S-PBN administered 5 min after SE onset exacerbated neuropathology in thalamic regions. In contrast, PBN and S-PBN administered as exposure treatment exacerbated neuropathology in thalamic and CA3 regions. The differential neuroprotective effects of PBN and S-PBN may be the result of the poor brain penetration by S-PBN. The results suggest that free radical scavenger activity is neuroprotective in cortical regions during cholinergic convulsions. Regional variations in drug-induced neuroprotectant activity in Li-pilo SE are common and suggest multiple mechanisms of neuropathology.