Effects of HI-6 on brain neuronal RNA and acetylcholinesterase: metabolic responses during acute soman intoxication.

Quantitative cytochemical techniques were used to monitor effects of the bis-pyridinium oxime HI-6 with and without atropine sulfate (AS) on soman-induced cerebrocortical (layer V) and striatal neuron RNA and acetyl-cholinesterase (AChE) impairments. In addition, plasma cholinesterase (ChE) activity was measured to determine the extent of peripheral enzyme reactivation. Antidotal pretreatment effected complete (HI-6) or partial (AS) amelioration of neuronal RNA depletion evidenced following 1.5 LD50 (195 micrograms/kg) soman, whereas combined HI-6 + AS treatment only partially restored (cortical) or did not change (striatal) neuron RNA contents. HI-6 produced appreciable plasma ChE reactivation but brain AChE activity was not significantly altered. In rats treated only with antidotes, HI-6 or AS alone significantly reduced neuronal RNA in both brain regions. These data indicate that HI-6 influences the metabolic status of central cholinergic compartments and can completely protect against soman-induced neuronal RNA depletion. However, there are no precise relationships among RNA restitution, AChE reactivation or the protective potency of antidotal treatments. Effects of HI-6 on neuronal RNA may signify central cholinolytic activity in vivo, but indirect effects mediated by peripheral mechanisms can not be excluded at present.