The effects of bilateral vagotomy on substance P-like immunoreactive nerves in the cardiac ganglia of the monkey (Macaca fascicularis)

The present study showed that neural degeneration occurred in the cardiac ganglia after bilateral vagotomy. At 1 week after operation, a majority of the substance P-like immunoreactive (SP-IR) nerve fibres were affected and they showed signs of degeneration. SP-IR nerve endings forming the pericellular baskets around seemingly normal neuronal cell bodies were also degenerated. By 2 weeks after operation, numerous macrophage-like cells infiltrated the cardiac ganglia and they engulfed the degenerating SP-LR cellular debris. At 3 months after operation, a few fine SP-IR nerve fibres were detected in the cardiac ganglia, together with a few small solitary SP-IR neurons. At 6-12 months after operation, numerous SP-IR nerve fibres were observed in the cardiac ganglia. Some of the SP-IR nerve endings started to form pericellular baskets around the seemingly normal neuronal cell bodies. It is concluded that there is reinnervation of the heart by SP-IR nerve fibres after surgical interruption to both vagi. However, the origin of these SP-LR nerve fibres and terminals remains unknown.