Organophosphate (OP) induced
seizures are commonly treated with
anticholinergics,
oximes and
anticonvulsants. Inhibition of
P-glycoprotein (PgP) has been shown to enhance the efficacy of
nerve agent treatment in
soman exposed rats. In the present study, the promising effects of the PgP inhibitor
tariquidar were investigated in more detail in rats s.c. exposed to 150 μg/kg
soman. Treatment with
HI-6 and
atropine sulfate (125 and 3 mg/kg i.m respectively) was administered 1 min after exposure.
Diazepam (0.5 mg/kg i.m.) and/or
tariquidar (7.5 mg/kg i.v.) were included either at 1 min or 40 min following onset of
seizures. Animals that received
tariquidar, in addition to
HI-6 and
atropine, at 1 min, displayed a rapid normalization of EEG activity and cessation of seizure-associated behaviour. This improvement by addition of
tariquidar was even more substantial in animals that also received
diazepam, either immediately or delayed. Animals exhibiting lower intensity
seizures displayed less severe neuropathology (neuronal loss, microglia activation and
astrogliosis), primarily in the piriform cortex, and to a lesser extent amygdala and entorhinal cortex. The present findings suggest that the interaction of
tariquidar with
atropine may be the decisive factor for enhanced treatment efficacy, given that
atropine was previously found to be a PgP substrate. A more thorough understanding of the interactions of
nerve agent antidotes, in particular the actions of central
anticholinergics with
benzodiazepines, could contribute to a future optimization of treatment combinations, particularly those aimed at later stage medical interventions.