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Saliva has been collected from conscious rabbits in response to feeding pellets and carrots and amylase concentrations and flow-rates were measured. Saliva was collected from a polythene tube permanently inserted into the main duct, which, in most cases, kept patent for about a fortnight without any obvious decrease in the secretory capacity of the glands. 2. With pellets the flow-rate varied between 50 and 1250 microliter./min, and the corresponding amylase concentration was relatively constant around 250 units/ml. When carrots were fed, the flow-rates were about threefold lower, but the amylase concentration was raised to a mean value around 1000 units/ml. In spite of the differences in flow-rates, the two kinds of food promoted the same maximum output of amylase, and the output for both kinds of food promoted the same maximum output of amylase, and the output for both kinds of food was found to increase with the flow-rate. 3. The amylase concentration in the saliva decreased after pre- or post-ganglionic sympathetic denervation, reducing the output of amylase by about 50%. However, the amylase concentration was further lowered by beta-adrenoceptor block, which decreased the output by an additional 25%, suggesting that circulating catecholamines contributed to the secretion of amylase. 4. The fluid secretion in response to pellets and carrots was mainly dependent on parasympathetic activity, and for both kinds of food the range of flow-rates was unaltered by sympathectomy or beta-adrenoceptor block. However, at flow-rates below 50 microliter./min, where 25% of all samples with carrots were obtained, sympathetic activity may have contributed significantly to the fluid secretion. 5. In experiments on anaesthetized rabbits, frequency-response curves for amylase and fluid secretion in response to parasympathetic and sympathetic activation were obtained. A comparison between these observations and those obtained in the conscious animals during feeding suggests a parasympathetic activity mainly between 1 and 5 Hz and a sympathetic around 1 Hz. 6. It is concluded that both parasympathetic and sympathetic secretory nerves are reflexly activated during feeding, and that the normal secretion during a meal is dependent on an interplay between the nerves. The results suggest that at least two different afferent nervous pathways are involved in the control of the secretory nerves.

1. In dogs under chloralose-urethane anaesthesia secretion from the submandibular gland was recorded with the outflow at gland level and at heights of up to 50 cm above the gland.2. With the outflow level increased, secretion elicited by sympathetic nerve stimulation was far better maintained before than after injection of the alpha-adrenoceptor blocking agent dihydroergotamine.3. When the outflow level was raised while no secretion occurred, fluid flowed into the gland. Part of this amount was returned on lowering the outflow to gland level. This volume was assumed to have been accommodated in the distended luminal system, whereas some fluid was obviously lost into the gland tissues.4. Both these fractions of the fluid flowing into the gland when the outflow level was high could be reduced by injecting the alpha-receptor agonist phenylephrine. Bradykinin, which like phenylephrine is known to contract salivary myoepithelial cells, had the same effect on the two inflow volumes.5. It is concluded that myoepithelial contraction reduced the distensibility of the luminal system and in addition supported the acini, thereby diminishing backflow into the glandular tissues and enabling the gland to discharge saliva against a high pressure.6. Morphologically it was found that in resting glands PAS-positive saliva was displaced from the ductal system when the outflow cannula was raised, but it was preserved in the lumina under similar conditions when the myoepithelial cells were being stimulated by phenylephrine or bradykinin.7. Although sympathetic secretion could be maintained against a head of pressure, so long as it was accompanied by myoepithelial contraction, the increased force caused by the secretion led to disruptive damage of striated ducts which are the first part of the luminal system not supported by myoepithelial cells.8. The morphological findings reinforce the belief that contraction of myoepithelial cells gives active support to the underlying parenchyma.

1. In anaesthetized rabbits amylase secretion from the parotid gland was investigated. Secretion was evoked by sympathetic nerve stimulation, either alone or superimposed on a parasympathetic background secretion, imitating the resting secretion present in the waking animal.2. Sympathetic nerve stimulation at frequencies below 1 Hz was alone subthreshold for fluid secretion, but could greatly increase the amounts of amylase present in fluid secretion produced by parasympathetic nerve stimulation. The amylase output due to sympathetic nerve stimulation alone at 10 Hz did not exceed that seen in response to a stimulation at 1 Hz superimposed on parasympathetic activity.3. The amylase output in response to superimposed sympathetic stimulation was not influenced by the rate of fluid secretion, which was altered by stimulating the parasympathetic nerves at different frequencies.4. Sympathetically-evoked amylase secretion was abolished after beta(1)-block. The amylase secretion remaining on parasympathetic activation was sparse.5. It is concluded that secretion of amylase in response to sympathetic nerve stimulation requires the presence of a parasympathetic fluid secretion to be washed along the glandular ducts. Parasympathetic activity may also augment the sympathetic effect on amylase secretion.

1. In dogs under chloralose-urethane anaesthesia the submaxillary duct was cannulated and connected either to an open outflow system, in which saliva displaced water, or to a closed pressure recording system.2. The secretory cells, which are supplied with beta-adrenoreceptors, were stimulated with isoprenaline, adrenaline or sympathetic nerve stimulation. Myoepithelial cells, supplied with alpha-receptors, were activated with phenylephrine, adrenaline or sympathetic stimulation, and also with bradykinin. To abolish alpha-receptor stimulating effects of adrenaline and sympathetic nerve stimulation, dihydroergotamine, phenoxybenzamine and phentolamine were used.3. When the secretory cells were activated alone, saliva flowed from the salivary duct, but the flow started late and only a moderately high pressure could be produced in the closed system. Saliva appeared much earlier in the duct when secretion was combined with myoepithelial contraction, and a much higher pressure could be built up in the duct system.4. It is concluded that rapid emptying of saliva in the mouth and a maintained flow at a high rate of the viscous saliva is promoted by contractions of the myoepithelial cells.