Brain-derived neurotrophic factor (BDNF) is known to regulate synaptic transmission and plasticity. An acute application of BDNF to visual cortical and hippocampal slices is reported to enhance excitatory synaptic transmission when evaluated by either field potentials or single-cell excitatory postsynaptic currents (EPSCs). As field potentials mostly reflect activities of pyramidal neurons and EPSCs were recorded from pyramidal cell-like neurons, an important question of how BDNF acts acutely on excitatory synaptic transmission to GABAergic neurons has not been answered yet. To address this question, we used visual cortical slices prepared from glutamic acid decarboxylase 67-green fluorescence protein (GAD67-GFP) knock-in mice. In these slices, GABAergic neurons containing GAD67, GABA synthesizing enzyme, can easily be detected under a fluorescence microscope. So we could record EPSCs evoked by layer IV stimulation from GABAergic neurons in layer II/III of the cortex through whole-cell patch-clamp electrodes. We found that BDNF quickly depressed EPSCs in most GABAergic neurons and this depression lasted after cessation of the BDNF application. Questions of whether two subtypes of GABAergic neurons, parvalbumin-positive and -negative neurons, are affected in the same way, and the depression is pre- or postsynaptic in origin, are under investigation. [Jpn J Physiol 54 Suppl:S143 (2004)]
