Since urethane is a widely used anesthetic in animal experimentation, in the present study we evaluated its effects on neurons of the NTS in brainstem slices from young rats (25-30 days old). Using the whole-cell configuration of the patch-clamp technique, spontaneous postsynaptic currents (sPSCs) and evoked excitatory postsynaptic currents (eEPSCs) were recorded. Urethane (20 mM) decreased by about 60% the frequency of GABAergic sPSCs (1.0 ± 0.2 vs 0.4 ± 0.1 Hz), but did not change the frequency, amplitude or half-width of glutamatergic events or TTX-resistant inhibitory sPSCs (miniatures IPSCs). Miniatures IPSCs were measured in the presence of urethane plus 1 mM diazepam (1 mM) and no changes were seen in their amplitude. This suggests that the GABA concentration in the NTS synapses is set at saturating level. We also evaluated the effect of urethane on eEPSCs and no significant change was observed in the amplitude of NMDA [44.2 ± 11.5 vs 37.6 ± 10.6 pA, (holding potential = 40 mV)] and non-NMDA currents [204.4 ± 35.5 vs 196.6 ± 31.2 pA, (holding potential = -70 mV)]. Current-clamp experiments showed that urethane did not alter the action potential characteristics and passive membrane properties. These data suggest that urethane has an inhibitory effect on GABAergic neurons in the NTS, but does not change the spontaneous or evoked excitatory responses.