AbstractCytophotometric analyses of RNA and acetylcholinesterase responses of caudate and cerebrocortical neurons of soman toxicated rats were conducted to characterize impairments in regulatory aspects of neuronal metabolism occurring in the acute phase of cholinesterase impairment. There was a severe and dose‐dependent suppression (20–60%) in neuronal acetylcholinesterase activity in both a.m. and p.m.‐treated rats; no diurnal differences were apparent in control acetylcholinesterase levels or neuronal acetylcholinesterase responsiveness to soman toxication. RNA levels, however, were markedly higher in p.m. than in a.m. saline‐treated controls. Soman depressed caudate neuron RNA contents in the afternoon, but not in the morning. Cerebrocortical neuron RNA levels were suppressed in both a.m. and p.m.‐toxicated rats, although this RNA depletion was more severe in the afternoon. These results indicate that soman can elicit marked alterations in neuronal transcriptional‐translational capabilities and that there are diurnal variations in cellular metabolic responsiveness to soman toxication. Although functional relationships between soman‐induced cholinesterase inhibition and RNA depletion remain to be elucidated, depressed RNA metabolism appears to be a maladaptive response preventing rapid regeneration of cholinesterase follow