Figure 4.
The pharmacology of field potentials. A, Field potentials on a single electrode are reported from a sequential experiment in which, after a control period, drugs were added to the extracellular solution. The control field potentials are modified by application of 10 μm bicuculline. EPSP-like responses show a slow, smooth time course. In spiky responses, N2a peak is left unchanged by bicuculline, but N2b is markedly enhanced and is followed by oscillations, the first of which corresponds to N2b. B, In a different experiment than in A, after application of 10 μm bicuculline, N2b is enhanced. Then, subsequent application of the NMDA receptor blocker, 50 μm d-APV, reduces N2b. Addition of the AMPA receptor blocker, 10 μm NBQX, abolishes the postsynaptic field response. N1 is left unchanged by these receptor antagonists, confirming its presynaptic nature. Each trace in A and B is the average of 10 responses. C, Granule cell spikes were recorded in LCA before and after application of 10 μm bicuculline. In control, a delayed and scattered spike response is observed (open circles). After bicuculline application, the first spike anticipates and a second spike emerges (filled circles). The PSTH shows peaks corresponding to N2a and N2b.