Influence of thyroid function upon "Substance P" induced secretion of saliva by submaxillary glands.

The effects of changes in thyroid function on the action of "Substance P" upon the secretion of saliva by the submaxillary glands was studied in male Wistar rats, with parasympathetic decentralization on the left side. The dose-response curves to increasing doses of "Substance P" showed in hyperthyroid animals increased salivary secretion while in hypothyroid animals the dose-response curve to the drug was decreased. Every animal showed supersentivity to "Substance P" in the decentralized gland. The influence of changes in thyroid function in the denervated glands was the same as that in the unoperated side, increased salivary secretion in hyperthyroidism and decreased in hypothyroidism.

Thyroid hormone modulation of VIP's induced salivary secretion in the submaxillary glands of rats.

The effect of changes in thyroid function upon vasoactive intestinal peptide (VIP) induced secretion of saliva were studied in male Wistar rats. Hyperthyroidism was induced by the sc administration every 12 h of 10 micrograms/100 g bw of I-triiodothyronine; hypothyroidism was induced by surgical thyroidectomy 2 weeks before the experiments. Preganglionar parasympathetic denervation was induced by sectioning the chorda tympani on the left side. The dose-response curves to increasing doses of VIP showed in the hypothyroid animals increased salivary secretion, while in the hyperthyroid ones the dose-response to the drug was reduced. This effect was seen on both sides, the denervated and the control ones. In the denervated glands there was a marked hypersensitivity to the administration of VIP producing greater responses with the same doses, in the 3 groups of animals. The negative modulation by thyroid hormones of the salivary response to VIP administration is compared with the positive modulation they induce in the salivary response to beta-adrenergic and cholinergic drugs.