Structural changes associated with parotid “Degeneration secretion” after post-ganglionic sympathectomy in rats

Summary

Parotid glands of rat have been examined 12, 24 and 48 hours after avulsion of the cervical sympathetic ganglion and compared with the normally innervated left glands. Formaldehyde-induced fluorescence showed a relatively normal complement of adrenergic nerves at 12 hours but most of the nerves had lost their noradrenaline content by 24 hours and no fluorescent nerves were detected at 48 hours. Ultrastructural degenerative changes in axons were rare at 12 hours, common at 24 hours, and the degenerating axons appeared to have disappeared by 48 hours. The glands looked whitish and pale and similar to the controls at 12 and 48 hours but were pinkish and oedematous on the sympathectomised side at 24 hours. Correspondingly the acini were loaded with secretory granules at 12 and 48 hours but were extensively depleted of granules at 24 hours. This loss of granules is considered to be due to sympathetic “degeneration secretion” caused by the release of noradrenaline from the degenerating adrenergic nerves between 12 and 24 hours after ganglionectomy. This is thought to be the first example of morphological change resulting from “degeneration activation” to be recorded microscopically.