The regulation of parotid and submandibular salivary secretion in sheep

During eating the parotid and submandibular salivary glands of sheep are stimulated via parasympathetic and sympathetic pathways. The response of the glands depends on the nature of the diet and the duration of a meal. In anaesthetized animals a continual activity in the parasympathetic nerve supply to the parotid gland reflects the excitatory effects of rumino-reticular (gastric) distension and contraction. This activity is reduced by high levels of rumino-reticular distension and increased osmolality of venous blood. It is argued that in conscious sheep these factors are important in determining the volume of saliva that is normally produced. Mechanoreceptors in the parotid glands of sheep are also a source of considerable afferent activity. Some of these receptors are active during naturally stimulated secretion and it is suggested they may also have a role in regulating salivary gland function.