Functional and structural studies concerning the control of activity in zygomatic glands of cats.

The zygomatic gland of the cat consists of at least two parts, separated by a septum, and each drains by a separate duct opening on a mucosal ridge postero-medial to the parotid orifice. It is composed on thin-walled ducts and tubulo-acini, containing mainly mucous cells, but scattered cap cells are also present. In cats under chloralose anaesthesia there is a spontaneous flow of extremely viscous saliva and often, in addition, there is a reflexly elicited component to the secretion. In fact, in contrast to the other major salivary glands, the zygomatic gland is easily made to secrete reflexly even in deep] anaesthesia, e.g. by pinching ipsilateral parts of the tongue, by stimulation of the oesophagus mimicking swallowing, or by afferent excitation of ipsilateral lingual, glossopharyngeal or vagal nerves. The efferent link of the reflex arc is contained in the buccal branch of the mandibular nerve. Section of this nerve abolishes these reflexes, and two weeks later a great loss of acetylcholinesterase positive nerves can be demonstrated in the gland. Efferent stimulation of the buccal nerve evokes a lively secretion that is not affected by hexamethonium but is abolished by atropine. Histochemically, adrenergic nerves are also found surrounding the acini and these nerves disappear after excision of the superior cervical ganglion. Electrical stimulation of the cervical sympathetic trunk causes some secretion, mainly by way of beta 1-adrenoreceptors. Myoepithelial cells are present around the tubulo-acini, and indications of the effect caused by their contraction on the flow from the glands have been observed. Such activity can be induced reflexly and it is then abolished by cutting the buccal nerve or by injecting atropine.