Principal cells in lateral geniculate: effects of metrazol on capacity to after-discharge

The effect of metrazol on the capacity of dorsal lateral geniculate nucleus (dLGN) principal (P) cells to repetitively burst (after-discharge) following visual system stimulation was examined in P cells which differed in terms of response patterns to visual stimulation (latency of initial spike, extent of repetitive bursting, and on- or off-type responding cells). Twenty-seven P cells were examined in as many subjects. Metrazol augmented repetitive bursting irrespective of the type of P cell as long as repetitive bursting was present in the pre-metrazol period. P cells that displayed only a single initial burst to photic stimulation did not exhibit after-discharge bursting during the metrazol challenge. In all but one cell metrazol enhanced baseline firing rate. These results are discussed in terms of the putative nature of inhibition in the rat dLGN.