A, post-synaptic responses evoked by a train of 10 pulses to the MFB in a UBC showing both the early- and the late-onset response, in control condition (top trace) and after perfusion of APV plus NBQX in the bath (bottom trace). Note that the early-onset response was blocked by the NMDA/AMPA receptor antagonists, thus unmasking the late-onset response. The inset shows the stimulus region in greater detail, demonstrating abolition of EPSPs following drug perfusion. B, post-synaptic responses evoked by a train of 10 pulses to the MFB in a UBC showing only the late-onset response, in control condition (top trace) and after perfusion of MCPG in the bath (bottom trace). Note the lack of effect of MCPG.