The intravenous infusion of melatonin (5 and 25 mg/kg over 10 min) evoked a dose-dependent output of protein and amylase but no overt fluid secretion from the parotid gland of the pentobarbitone-anaesthetised rat, as revealed by increased concentrations of protein and amylase activity in a subsequent wash-out flow of saliva in response to an intravenous bolus injection of methacholine (5 microg/kg) 10 min later. The secretory responses to melatonin occurred in the presence of alpha- and beta-adrenoceptor antagonists. They were not affected by the cholecystokinin A-receptor antagonist, lorglumide, and they were reproduced in eviscerated animals acutely subjected to postganglionic sympathetic and parasympathetic denervation of the gland. The responses to melatonin were partially dependent on nitric oxide generation, through the activity of nitric oxide synthase of the neuronal type. Immunoblotting showed both melatonin receptors of type 1 and type 2 to be expressed in parotid gland tissue. The relative specific melatonin 2-receptor antagonist luzindole prevented the expected secretory effects of melatonin. The results favour a direct action by melatonin on melatonin receptors of parotid secretory cells and suggest a potential physiological role for melatonin in the regulation of salivary glandular activities.

中文翻译：

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褪黑素诱发了麻醉大鼠腮腺体内蛋白质和淀粉酶的分泌。

静脉注射褪黑激素（10分钟内分别为5和25 mg / kg）引起了蛋白质和淀粉酶的剂量依赖性输出，但戊巴比妥麻醉大鼠的腮腺没有明显的液体分泌，这是由蛋白质和静脉内推注乙酰甲胆碱（5 microg / kg）10分钟后，随后唾液冲洗流中的淀粉酶活性。对褪黑激素的分泌反应发生在存在α-和β-肾上腺素受体拮抗剂的情况下。它们不受胆囊收缩素A受体拮抗剂lorglumide的影响，并且在急性遭受神经节后交感神经和副交感神经去神经的内脏动物中繁殖。对褪黑激素的反应部分取决于一氧化氮的产生，通过神经元型一氧化氮合酶的活性 免疫印迹显示腮腺组织中同时表达了1型和2型褪黑激素受体。相对特异性的褪黑激素2受体拮抗剂Luzindole阻止了褪黑激素的预期分泌作用。结果支持褪黑激素对腮腺分泌细胞褪黑激素受体的直接作用，并暗示褪黑激素在调节唾液腺活动中的潜在生理作用。