The relationship between the amygdala and bed nucleus of the stria terminalis in the cat: an evoked potential and single cell study

The effects of amygdala stimulation on excitability of cells in the bed nucleus of the stria terminalis (BNST) were investigated in the cat. The predominant effect of stimulation was to excite cells localized in the lateral BNST. Cells responded either with single spikes to a stimulus pulse or in short bursts. Spontaneous firing of cells after a pulse to the amygdala was observed to both increase and decrease over a 4-s interval. Increases in firing rate, however, were the predominant response. Cells in more anterior locations in the BNST responded with latencies shorter than those of cells in more posterior locations, reflecting either differences in conduction time of excitation from the amygdala or differences in transmitters mediating the excitatory effects. Associated with increases in cell firing was a compound field potential with an initial negative component and a later positive component. These components may be generated by different cell types within the BNST. The negative component likely represents a field EPSP. Effective sites of amygdala stimulation were restricted to the posterior basal amygdala, and effects observed in the BNST were restricted to the lateral BNST. These data correspond well with anatomical studies showing a monosynaptic projection of basal amygdala to lateral BNST in the cat. This study suggests that this projection is predominantly excitatory.