Parasympathetic discharges evoked in the pelvic nerve by stimulation of various structures in the amygdala

Parasympathetic discharges evoked by application of single and paired stimuli to central, corticomedial, and basolateral nuclei of the amygdala were recorded from the pelvic nerve (PN) in anesthetized and immobilized cats. The discharges were found to include three main negative waves (I, II, and III waves, appearing with the latencies of 16.0–17.8, 74–87, and 171–184 msec, respectively). The first two waves were seen most regularly. Sometimes the I wave was preceded by a super-early negative component of a low amplitude appearing with a latency of 8.5–10.7 msec. The discharges evoked by stimulation of various nuclei of the amygdala did not significantly differ from each other in their thresholds, time courses, and amplitudes, which suggests a relatively diffuse distribution of parasympathetic efferent structures in the amygdala. It was shown, using paired stimuli, that a response to the second stimulus needed a long-lasting period (a few tens of milliseconds) to be restored. The origin of the components of the amygdalofugal parasympathetic discharges recorded from the PN, as well as the corresponding pathways they spread through, are discussed. In addition, the possible origin of the positive components of the PN discharges are considered.Neirofiziologiya/Neurophysiology, Vol. 26, No. 5, pp. 326–333, September–October, 1994.