Changes in the physiology and fine structure of the taenia of the guinea-pig caecum following transplantation into the anterior eye chamber.

1. The taenia of the guinea-pig caecum has been used as a model to study the re-establishment of autonomic innervation following transplantation into the anterior eye chamber. The ultrastructure, the histochemical localization of noradrenaline and acetylcholinesterase and the pharmacology of transmission to the taenia have been examined 1 day to 16 weeks following transplantation. Both ganglion-free strips of the taenia and caecal wall segments including the underlying Auerbach's plexus were used.2. Caecal wall preparations: nerve fibres from intramural ganglion cells retracted during the first 2 days following transplantation, but reappeared in the muscle soon afterwards. Adrenergic nerves from the iris formed terminals about ganglion cells at about 2-4 weeks. Both cholinergic excitatory and non-adrenergic (;purinergic') inhibitory transmission to the muscle was re-established by 2-4 days following transplantation.3. Taenia strip preparations: both adrenergic and cholinergic nerve fibres were demonstrated histochemically in muscle bundles by 2-4 weeks. Non-adrenergic inhibitory and cholinergic transmission was not re-established until 2-4 weeks following transplantation. There was an abnormally dense re-innervation of the muscle by adrenergic nerve fibres by about 8 weeks which is compared with the innervation of aganglionic bowel in Hirschsprung's disease.4. The origin of non-adrenergic inhibitory responses in the transplanted taenia is discussed and the results considered in relation to the re-innervation of transplants of the vas deferens and of intestine during early development.