Anxiolytic-like effect of hydrogen sulfide (H2S) in rats exposed and re-exposed to the elevated plus-maze and open field tests

Hydrogen sulfide (H2S), an endogenous gaseous mediator, modulates many physiological functions in mammals but evidence of its involvement in emotional and behavioral aspects is currently scarce. We hypothesized that this gas plays a modulatory role in behavioral parameters in rats submitted to tests (for 5 min) in the open field (OF) and elevated plus-maze (EPM - test and retest). Male Wistar rats (200-250 g) were intraperitoneally injected with saline or Na2S (a H2S donor; 4, 8 and 12 mg/kg) either once or for 8 days, and submitted to the OF test or to the EPM test and retest. A third group (naïve) was not injected but exposed to the same experimental protocols. In the OF test, Na2S injected for 8 days caused a decrease in self-cleaning (4, 8 and 12 mg/kg) and freezing behaviors (8 and 12 mg/kg), and a rise in the rate of line crossings in the central part of the arena (12 mg/kg). In the EPM test and retest, Na2S at 12 mg/kg for 8 days caused an increase in the number of open arm entries and in the percentage of time spent on open arms. Our data are consistent with the notion that H2S exerts anxiolytic-like effects in rats submitted to the EPM and OF tests. Moreover, this gaseous modulator reduces aversive learning in the EPM retest.