Transneuronal changes in the myenteric ganglia of the monkey following vagotomy

This study describes the ultrastructural changes in the myenteric ganglia at the gastro-oesophageal junction of the monkey (Macaca fascicularis) after unilateral cervical vagotomy. Degenerating vagal fibres occurred within the ganglia and they represented only a small fraction of the endings present. The most striking finding at days 1-3 after vagotomy, was that some dendrites of myenteric neurons had a distinctly increased electron density which ranged from a moderate darkening of the cytoplasm to an almost complete blackening of the profile. This regressive change was widespread; however, apparently, it did not affect more than one dendrite in any neuron. Darkened dendrites were no longer found at 5-7 days after vagotomy, and they were not present in control ganglia. It is concluded that the degeneration of vagal endings is accompanied by transneuronal regressive changes that are very rapid in onset, are short lasting and possibly fully reversible, and affect only one dendrite of the neuron. It is suggested that the process observed represents a novel form of transneuronal influence.