The iGABASnFR is a genetically encoded optical sensor that can detect the inhibitory neurotransmitter GABA. Its recent improvements have allowed it to reliably monitor GABA release evoked by electric stimulation (Marvin et al., Nature Methods 2019) or epileptiform activity (Magloire et al., Curr Biol. 2023). Here, we employed iGABASnFR2, both neuronal and astrocytic variants, virally expressed in the hippocampus or somatosensory cortical region for ~4 weeks of in vivo transduction for high-resolution multiplexed two-photon excitation imaging in acute hippocampal slices or in the barrel cortex in vivo. We report the ability of iGABASnFR2 to detect GABA release from individual axonal boutons evoked by neuronal depolarization, i.e. firing of a single interneuron in the whole-cell configuration, in acute brain slices. In the somatosensory cortical region, we could monitor GABA release events from multiple axons in response to physiological sensory stimuli, i.e. brief whisker stimulation in vivo. Thus, our data revealed the capability of iGABASnFR2, expressed at a sufficient level in either neurons or astrocytes, to detect GABA release events in physiological conditions.