Abstract

The chronic supersensitivity of the submaxillary gland to secretory agents was studied after chemical or surgical sympathectomy. Twenty days after either procedure, a marked supersensitivity to norepinephrine or isoproterenol, but not to metilacholine, was found. In surgically denervated glands, supersensitivity to norepinephrine or isoproterenol persisted for the following 40 days. On the other hand, the 6-hydroxydopamine (6-OHDA)treated rats showed a marked decline in the supersensitivity during this period although at the 60th day the secretory responses were still greater than in the corresponding controls. Cocaine administration potentiated the responses to norepinephrine in normal or in 6-OHDA- treated animals while such effect. was not obtained in surgically denervated glands. Neuronal accumulation of ³H-norepinephrine in vivo was similar in controls and in 6-OHDA-treated glands at 20 or 60 days after drug administration. Yet at these times endogenous norepinephrine levels were about 40 and 80% of the controls, respectively. Surgically denervated glands showed a long-lasting depletion of norepinephrine stores and abolition of neuronal accumulation of ³H-norepinephrine. Tile accumulation of (-)-³H-norepinephrine in vitro was inhibited in the chemically sympathectomized glands by only 30%. Cocaine had the same inhibitory potency on neuronal uptake of norepinephrine in controls and in 6-OHDA-treated rats. It is suggested that the residual supersensitivity seen in the 6-OHDA-treated glands after reinnervation is due to postsynaptic changes.