The effect of neonatal sympathectomy on the response of the rat submandibular gland to isoproterenol.

The right superior cervical ganglion was removed from 1-day-old rat pups. For four consecutive days (22-26 days of age), the rats were injected twice daily with isoproterenol-HCl (IPR) at a dose of 2.0 mg/100 g.b.w. and killed on the 27th day of age. Control animals were injected with the solvent, 0.1% Na2S2O5, according to the same protocol. In both control and IPR-treated rats, fluorescence microscopic examination of glands prepared by the Falck-Hillarp method showed a total absence of adrenergic nerve fibers on the side of sympathectomy, and a normal innervation on the unoperated side, while light microscopic examination of Epon-embedded glands revealed no differences in structure between the noninnervated and intact glands. However, after IPR treatment the noninnervated glands consistently showed greater absolute and relative weight, and total DNA, RNA and protein than the corresponding intact gland from the same animal. It is suggested that this greater hyperplastic and hypertrophic response in the noninnervated gland represents a postjunctional supersensitivity of acinar cells to the beta agonistic action of IPR.