Electron microscopic and autoradiographic studies of the myenteric ganglia of the ferret stomach after highly selective vagotomy

ABSTRACT

In this study, the preganglionic fibres of the vagus nerve were investigated in the myenteric ganglia of the ferret stomach three and four months after highly selective vagotomy. Autoradiographic technique at the electron microsscopic level was used to analyze the vagal nerve terminals after injection of tritiated leucine as an anterograde labeling tracer into the vagal dorsal motor nucleus. Electron microscopic examination of the body of the stomach of control animals showed normal ulrastructure of the myenteric ganglia and labeled nerve fibres were seen distributed in the myenteric ganglia of the body and pyloric areas of the stomach. In the acute experimental animals injection of tritiated leucine was carried out immediately after surgery. After 48 hours survival period, electron mictoscopic examination of the body of the stomach showed no morphological changes, and no labeled nerve fibres as a results of highly selective vagotomy while the pylorus showed many labeled nerve fibres. In the chronic experiments, the animals were left to survive for three months after highly selective vagotomy. After injection of tritiated leucine and analysis by autoradiography, two important findings were observed in the denervated areas of the body of the stomach [i] Morphological changes affecting the ganglionic cell bodies, axons and nerve terminals [ii] Re-appearance of labeled nerve fibres in the body of the stomach. Interstingly, electron microscopic examination of the same areas of the body of the stomach four months after highly selective vagotomy showed normal ultrastructure of the myenteric ganglia with labeled nerve fibres in the same areas. It is concluded that the deprivation of the preganglionic input to the myenteric ganglia produced trans-synaptic neurological changes. These morphological degenerative changes disappeared when the stomach was re-innervated. Re-appearance of the labeled nerve fibres in the denervated areas of the stomach is due either to regeneration of the cut branches of the vagal nerve or due to the sprouting of the intact vagal nerve terminals which spread from the pyloric areas to innervate the denervated areas of the body of the stomach. This phenomenon of sprouting of the intact vagal nerve terminals or regeneration of the cut nerves, which was demonstrated by autoradiography at the electron microscopic level may explain the recovery of gastric function after vagotomy and may account for the failure of vagotomy for the treatment of peptic ulcer patients. It also could reduce the need for surgical intervention in peptic ulceration