Connectivity between brainstem autonomic structures and expression of c-fos following electrical stimulation of the central nucleus of the amygdala in rat

Combinations of retrograde tracing with detection of Fos (the protein product of the immediate early gene c-fos) following electrical stimulation of the central nucleus of the amygdala were used to explore: (1) the connectivity of activated (Fos-positive) neurons in the ventrolateral medulla with the nucleus of the solitary tract; (2) the connectivity of activated neurons in the nucleus of the solitary tract with the ventrolateral medulla; (3) the proportion of activated catecholaminergic neurons that project to the nucleus of the solitary tract or to the ventrolateral medulla. Retrograde tracer was injected into the nucleus of the solitary tract or the ventrolateral medulla. After 5 days, stimulation for 60 min induced a statistically significant increase in the number of Fos-immunoreactive neurons in the ventrolateral medulla that project to the nucleus of the solitary tract and in the number of Fos-positive neurons in the nucleus of the solitary tract that project to the ventrolateral medulla. Of the neurons activated by stimulation of the central nucleus of the amygdala, 20% in the ventrolateral medulla and 3% in the nucleus of the solitary tract contained the retrograde tracer and were also immunopositive for tyrosine hydroxylase, the enzyme responsible for synthesis of catecholamines.