Muscarinic receptor immunoreactivity in the superior salivatory nucleus neurons innervating the salivary glands of the rat

► The superior salivatory nucleus (SSN) contains parasympathetic preganglionic neurons. ► SSN neurons innervating the salivary glands have muscarinic acetylcholine receptors. ► The muscarinic receptors in SSN neurons may be associated with the circadian rhythm. ► Sialogogues may act on the muscarinic receptors in SSN neurons.