Degeneration secretion and noradrenaline disappearance in rat salivary glands following proximal or distal axotomy.

The noradrenaline (NA) content and the degeneration secretion of saliva were studied in rat salivary glands, following proximal or distal sympathetic denervation. Proximal denervation was obtained by removal of the cervical superior ganglion, which left a long stump of adrenergic axons attached to the gland. Distal denervation was achieved by crushing the perihilar tissue, including the adrenergic axons, close to the gland, leaving only short axon stumps connected with the gland. Onset of both NA decrease and degeneration secretion occurred first in the distally denervated glands and about 2 h later on the proximally denervated sides. Except for the delay of 2 h the pattern of NA decrease and saliva secretion was similar after the two denervation procedures. The length of the attached axon stumps was estimated to be about 15-20 mm longer on the proximally denervated side. Therefore, the delay of 2 h caused by this length of axons corresponds to the proximo-distal intra-axonal transport distal to the "axotomy" of some protecting factors at the rate of 8-10 mm/h. Onset of degeneration secretion was observed between 11 and 12 h after proximal denervation when the NA content was decreased by about 10%. The maximum of saliva secretion occurred about 14 1/2 h after denervation when only 45% of the NA remained in the gland. The correlation between the degeneration secretion of saliva and the decrease in NA probably was due to 1) the amount of NA leaking from degenerating nerve terminals, and 2) the inactivation of this escaped NA by the re-uptake mechanism in the membrane of still intact nerve terminals.