Synaptic currents (PSC) evoked in hippocampal neurons by stimulation of Schaffer collateral are the sum of excitatory (EPSC) and inhibitory (IPSC) components. Inhibition of glutamate or GABA receptors is used for separation of the components (Karnup & Stelzer, 1999). However, such treatment affects the communication network in the slice. We employed an approach based on the difference in the reversal potentials of glutamate-gated and GABA-gated currents (Quardouz & Lacailee, 1997). Transverse slices were prepared from brains of rats decapitated under urethane anaesthesia (1g/kg, i.p.). The pipette solution for patch clamp recording contained (mM): K-gluconate-130, NaCl-5, MgCL2-2, CaCl2-1, HEPES-KOH-10, EGTA-10, MgATP-2, QX-314chloride-6. NMDA receptors were inhibited by APV. Under these conditions the reversal potential for the glutamate-gated current is about 0mV and for the GABA-gated current is about -40mV. The current-voltage curves are linear at negative voltages. PSC from pyramidal cells and interneurons in the slice at -40mV, (close to IPSC equilibrium potential) represent EPSC(-40). PSC at -80mV, is the sum of the doubled EPSC(-40) and the IPSC(-80). This allows us to obtain IPSC(-80) as PSC(-80)-2*PSC(-40). Importantly, both EPSC(-40) and IPSC(-80) are 40mV away from their reversal potential. Thus, our approach allows separate analysis of EPSC and IPSC without pharmacological treatment. The approach was tested by analysis of the action of GABA_A receptor antagonist bicuculline. Bicuculline (10 μM) inhibited 80-90% of calculated IPSCs without significant effect on EPSCs. In the pyramidal neurons both EPSCs and IPSCs were well pronounced (the ratio of amplitudes is 1.47, n=17). In contrast, in interneurons EPSC/IPSC was 2.3 on average. In 8 from 18 cells tested the inhibitory currents were negligibly small. This difference correlates with the ratios of glutamate- and GABA-evoked currents in isolated pyramidal neurons (1.1, n=14) and interneurons (1.8, n=31). IEM-1460, a dicationic derivative of adamantine is known as selective channel blocker of Ca2+-permeable AMPA receptors (Magazanik et al., 1997). Using the approach for separate analysis of EPSC and IPSC we found that IEM-1460 does not affect both these components in hippocampal pyramidal neurons. It means that inhibitory interneurons, which form synapses on the pyramidal neurons, express low-sensitive GluR2-containing AMPARs. Contrary, recordings from interneurons of CA1 area revealed that IEM-1460 significantly reduces both EPSC (40 ±2%, n=7) and IPSC (49±13%, n=8). It is suggested that hippocampal interneurons expressing GluR2-lacking AMPARs inhibit other interneurons rather than pyramidal neurons.