Parotid secretion of fluid and amylase in rabbits during feeding.

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Abstract
Saliva was collected from conscious rabbits in response to feeding pellets and carrots and amylase concentrations and flow rates were measured. With pellets the flow rate varied between 50-1250 .mu.l/min and the corresponding amylase concentration was relatively constant around 250 units/ml. When carrots were fed, the flow rates were about 3-fold lower, but the amylase concentration was raised to a mean value around 1000 units/ml. In spite of the differences in flow rates, the 2 kinds of food promoted the same maximum output of amylase and the output for the 2 kinds of food was found to increase with the flow rate. The amylase concentration in the saliva decreased after pre- or postganglionic sympathetic denervation, reducing the output of amylase by about 50%. The amylase concentration was further lowered by .beta.-adrenoceptor block, which decreased the output by an additional 25%, suggesting circulating catecholamines probably contributed to the secretion of amylase. The fluid secretion in response to pellets and carrots was mainly dependent on parasympathetic activity and for the 2 kinds of food the range of flow rates was unaltered by sympathectomy of .beta.-adrenoceptor block. At flow rates below 50 .mu.l/min, where 25% of all samples with carrots were obtained, sympathetic activity may have contributed significantly to the fluid secretion. In experiments on anesthetized 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 1-5 Hz and a sympathetic around 1 Hz. Parasympathetic and sympathetic secretory nerves are apparently, reflexly activated during feeding. The normal secretion during a meal is apparently dependent on an interplay between the nerves. At least 2 different afferent nervous pathways are probably involved in the control of the secretory nerves.