Fig. 1

Experimental protocols used in most of the experiments. During each sweep a presynaptic neuron was stimulated twice, firstly when the membrane potential in the postsynaptic cell was clamped 10-15 mV below PSC reversal potential for a given synaptic connection (typically –45 mV), and secondly when the membrane potential was shifted by 20 mV (typically to –25 mV). Sweeps were collected every 4 seconds. Stimulations of a presynaptic neuron are marked by arrows. Voltage in the postsynaptic neuron is schematically shown in upper panels, and currents in the lower. a Experimental protocol used in most of the experiments with 5b. b Experimental protocol used in the experiments with amiloride and diminazene. This protocol is similar to that shown in A, but during each sweep a pre-synaptic neuron was stimulated three times – two currents were recorded as inward and one as outward. The upper panel illustrates voltage protocol, and the lower panel currents recorded in a postsynaptic neuron