Response of single units in the amygdala to stimulation of buffer nerves in cat

Electrical activity of spontaneously active units in the amygdala of 19 chloralose-anesthetized cats was monitored for changes in firing frequency during electrical stimulation of the carotid sinus (CSN) and aortic depressor (ADN) nerves. Stimulation of the CSN altered the firing frequency of 30% (73/241) of the units on both sides of the amygdala. Of these units, 47% were excited and 53% were inhibited. Stimulation of the ADN elicited a change in firing frequency of 20% (50/251) of ipsi- and contralateral units. Of these, 68% were excited and the remainder were inhibited. The average latency for all CSN responses (53 +/- 4.0 ms) was significantly longer than the average latency for ADN responses (35 +/- 3.3 ms). The majority of the responsive units were located in the central and lateral nuclei of the amygdala. Spontaneously firing units responding to both CSN and ADN stimulation were found infrequently (7%, 14/188). These results indicate that the two buffer nerves project to specific regions within the amygdala, but the CSN and the ADN follow separate pathways probably involved in reflex arcs mediating different physiological responses.