Figure 5. Synaptic responses do not have an NMDA receptor component.

A and B, average evoked glutamatergic synaptic responses in the presence of bicuculline (10 μM) with minimal stimulation. ⋆marks the stimulus artefact. A, currents recorded when the membrane potential was held at +60, +30, -30 and -60 mV with 1 mM extracellular Mg²⁺. B, average evoked currents recorded when the membrane potential was held at +60, +30, -30 and -60 mV with no Mg²⁺ added to the extracellular solution. CNQX (20 μM) abolished the evoked glutamatergic synaptic currents. C, spontaneous glutamatergic currents recorded in the normal extracellular solution containing Mg²⁺. The membrane potential was held at 60, 40, -30 and -60 mV. D, evoked glutamatergic synaptic responses in the presence of bicuculline (10 μM) with multiple fibre stimulation. Low stimulation is 22 V, high stimulation is 50 V. Currents were recorded at a membrane potential of -60 and +60 mV. CNQX (20 μM) abolished the evoked glutamatergic synaptic currents. E, raw data showing evoked P2X receptor-mediated synaptic currents in the presence of CNQX (20 μM) and bicuculline (20 μM). Recording of superimposed traces at membrane potentials of ±60 mV. Note the similar decay time at both membrane potentials showing a lack of any NMDA receptor-mediated component.