Galantamine prevents long-lasting suppression of excitatory synaptic transmission in CA1 pyramidal neurons of soman-challenged guinea pigs

• Soman, an irreversible AChE inhibitor, is a potent neurotoxicant.
• Soman suppresses glutamate synaptic transmission in CA1 pyramidal neurons.
• Galantamine prevents soman's effect on glutamate synaptic transmission.
• Galantamine is an effective antidote for soman-induced long term cognitive deficits.

Galantamine, a drug currently approved for the treatment of Alzheimer's disease, has recently emerged as an effective pretreatment against the acute toxicity and delayed cognitive deficits induced by organophosphorus (OP) nerve agents, including soman. Since cognitive deficits can result from impaired glutamatergic transmission in the hippocampus, the present study was designed to test the hypothesis that hippocampal glutamatergic transmission declines following an acute exposure to soman and that this effect can be prevented by galantamine. To test this hypothesis, spontaneous excitatory postsynaptic currents (EPSCs) were recorded from CA1 pyramidal neurons in hippocampal slices obtained at 1 h, 24 h, or 6–9 days after guinea pigs were injected with: (i) 1×LD50 soman (26.3 μg/kg, s.c.); (ii) galantamine (8 mg/kg, i.m.) followed 30 min later by 1×LD50 soman, (iii) galantamine (8 mg/kg, i.m.), or (iv) saline (0.5 ml/kg, i.m.). In soman-injected guinea pigs that were not pretreated with galantamine, the frequency of EPSCs was significantly lower than that recorded from saline-injected animals. There was no correlation between the severity of soman-induced acute toxicity and the magnitude of soman-induced reduction of EPSC frequency. Pretreatment with galantamine prevented the reduction of EPSC frequency observed at 6–9 days after the soman challenge. Prevention of soman-induced long-lasting reduction of hippocampal glutamatergic synaptic transmission may be an important determinant of the ability of galantamine to counter cognitive deficits that develop long after an acute exposure to the nerve agent.