Parotid secretion of fluid and amylase in rabbits during feeding.

Abstract

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.

Influence of circulating catecholamines on protein secretion into rat parotid saliva during parasympathetic stimulation.

“…Stimulation of adrenergic receptors, however, need not be due solely to direct neural stimulation. In the rabbit, circulating catecholamines appear to cause release of small amounts of amylase during parasympathetic stimulation (Asking & Gj6rstrup, 1980;Gjorstrup, 1980). The effects of bilateral adrenalectomy in the rat demonstrate that circulating catecholamines in intact animals are responsible for a substantial portion of the amylase and peroxidase secreted in response to parasympathetic nerve stimulation of the parotid gland in this species.…”

“…In the rabbit, circulating catecholamines have recently been shown to influence parotid secretion in response to parasympathetic stimulation (Asking & Gjorstrup, 1980;Gjorstrup, 1980). Thus, circulating catecholamine, either from the adrenal glands or adrenergic nerve terminals, might be responsible for a portion of the protein secretion observed in rat parotid saliva following auriculotemporal nerve stimulation.…”

Β‐adrenergic Effects on Composition of Parotid Salivary Secretion of Sheep on Feeding

“…These increases are due in part to sympathetic stimulation; they were shown to be reduced, but not abolished, bypre-or post-ganglionic sympathectomy. An effect ofcirculating catecholamines was also proposed by Gjorstrup (1980a) since a further reduction in amylase secretion occurred when propranolol was given to rabbits subjected to cervical sympathectomy.…”

The possible relation between mastication and parotid secretion in the rabbit.

“…The results are compatible with the hypothesis that intra-oral mechanoreceptors may be involved in a masticatory-salivary reflex. Gjorstrup (1980a) reported that in conscious rabbits the output of parotid saliva was approximately three times greater when the animal chewed standard laboratory pellets (range 45-1260 #I/min) than when they chewed carrots (11-425 Il/min). In these experiments he collected saliva from the right parotid gland into small test tubes attached behind the animal's ear and calculated the rate of flow per minute from 2-3 min samples collected for amylase determination.…”