REGULATION OF AUTONOMIC RECEPTORS IN RAT SUB-MANDIBULAR GLAND

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 21  (1) , 27-35
Abstract
The binding of receptor specific radioligands to autonomic receptors in the rat submandibular gland was characterized after chronic drug administration and surgical sympathetic denervation. Reserpine administration resulted in an up-regulation of both .alpha.2-adrenergic receptors labeled by [3H]clonidine and .beta.1-adrenergic receptors labeled by [3H]dihydroalprenolol. The increase in .alpha.2-receptors was half-maximal 24 h after a single injection of reserpine, and was .apprx. 10-fold greater than control after 7 daily injections. The .beta.-adrenergic receptor density was the same as control after 3 days of reserpine administration, but within 7 days was .apprx. 2-fold greater than control. Guanethidine or yohimbine administration also resulted in an up-regulation of .alpha.2-adrenergic receptors. Reserpine administration of unilateral superior cervical ganglionectomy increased the density of .alpha.1-adrenergic receptor binding sites 24-80%. Norepinephrine and methoxamine, but not clonidine, caused K+ released from submandibular gland slices. Prazosin, but not yohimbine, blocked this response to norepinephrine, indicating that the response was mediated by .alpha.1-adrenergic receptors. K+ release elicited by .alpha.1-agonists was augmented in slices from animals that received reserpine. Neither drug treatment nor sympathetic denervation altered muscarinic cholinergic receptor binding. The densities of muscarinic and .beta.-adrenergic receptors were 23-51% higher in glands from female rats than in glands from male rats.