Neurotoxicological effects associated with short-term exposure of Sprague-Dawley rats to hydrogen sulfide

Although hydrogen sulfide (H2S) is a known neurotoxic hazard, only a limite d number of experimental animal studies have examined its neurochemical or behavioral effects. Our aim was to determine if short-term inhalation expos ure of rats to H2S would result in altered brain catecholamine levels or im paired learning and memory. Three groups of adult male CD rats were tested; two groups were exposed by nose-only inhalation (0, 30, 80, 200, or 400 pp m H2S) and one group was exposed by whole-body inhalation (0, 10, 30, or 80 ppm H2S) for 3 h per day for five consecutive days. The first group (n = 1 0 rats per concentration) was tested immediately following each daily nose- only H2S exposure for spatial learning with a Morris water maze. Core body temperatures were also monitored in these animals during and after the last H2S exposure. The second group of rats (n = 10 rats per concentration) was tested for spontaneous motor activity immediately following the fifth expo sure. These rats were then euthanized and striatal, hippocampal, and hindbr ain catecholamine levels determined. A third group of rats (n = 5-7 rats pe r concentration) was pretrained on a multiple fixed-interval (FI) schedule and exposed whole-body. Daily performance on the FI schedule was compared f or the week pre-exposure, for the exposure week immediately following daily exposures, and for the week postexposure. We observed significant reductio ns in motor activity, water maze performance, and body temperature followin g exposure only to high concentrations (greater than or equal to 80ppm) of H2S. Exposure to H2S did not affect regional brain catecholamine concentrat ions or performance on the FI schedule. Additional studies using other meas ures of behavior and longer-term exposure to H2S may be required to more de finitively address conditions under which H2S exposure results in behaviora l toxicity. (C) 2001 Elsevier Science Inc. All rights reserved.