Secretion of parotid acinar granules in rats during reflex stimulation after chronic sympathectomy

After chronic post-ganglionic sympathectomy the ultrastructure of 'resting' parotid acinar cells in rats remains relatively normal, despite the loss of nerve impulses normally causing secretion of acinar granules from this gland. The question whether eating hard chow still induces some acinar degranulation weeks after superior cervical ganglionectomy, has now been tested. It was found that scattered pockets of parotid acinar degranulation did occur. Some of these changes after unilateral denervation may have been attributable to intact sympathetic nerves arising from the contralateral superior cervical ganglion (Alm, Asking, Emmelin & Gjörstrup, 1984), but this cannot explain similar changes that occurred in glands after bilateral ganglionectomy. The possibility that some degranulation may be induced by circulating catecholamines was tested, 9-16 weeks after unilateral sympathectomy, by placing animals in the cold (0-4 degrees C) for 2 h before removal of tissues. Animals not given food during that time showed no evidence of parotid acinar degranulation, but those given hard chow showed extensive acinar degranulation in both parotid glands. On the sympathectomized side the degranulation was, however, less uniform and more patchy than on the side with an intact innervation. These findings agree with he belief that circulating catecholamines can, at times, induce degranulation of parotid acinar cells made supersensitive by chronic sympathetic denervation but, for it to occur, the cells must also be receiving parasympathetic stimulation at the same time. This interaction probably permits a sufficient turnover of granules to maintain a relative homoeostasis of the parotid acinar cells in rats.