Basal levels of noradrenaline, dopamine, 5-hydroxytryptamine, and acetylcholine in the submandibular, parotid, and sublingual glands of mice and rats

The salivary glands of 5-week-old mice and rats were divided into submandibular, parotid, and sublingual and analysed to determine basal levels of the neurotransmitters noradrenaline (NE) and acetylcholine (ACh) and the possible neurotransmitters dopamine (DA) and 5-hydroxytryptamine (5-HT), using a combination of high-performance liquid chromatography coupled with coulometric and amperometric detection and a direct injection technique employing crude homogenate supernatants. In both species, levels of NE were higher in the submandibular than in the other salivary glands, whereas levels of ACh were higher in the mouse submandibular and the rat sublingual glands than in other glands. In all the salivary glands, levels of DA were markedly lower than those of other target substances. Levels of 5-HT were similar in all salivary glands. These results show that in mouse and rat salivary glands, species differences in neurotransmitter distribution are relatively small, whereas there are considerable differences in distribution between the salivary glands.