Spontaneous salivation in the rabbit submandibular gland

Abstract

summABY 1. Salivation has been studied in the submandibular gland of the rabbit. A very slow spontaneous salivation took place when all possibility of nerve influence had been excluded. Salivation was not due to ultrafiltration.2. The 'spontaneous' saliva had a mean K concentration of 148 mM and Na concentration of 46 mm. With increasing salivation rate produced by parasympathetic nerve stimulation, K concentration fell to a plateau level of about 30 mm whilst Na concentration fell rapidly to reach the low value of 3 mM, then began to rise again at the higher flow rates.3. Ligation of the submandibular duct produced a reversal of the ion concentrations in spontaneous saliva. By 4 days K concentration was lower and that of Na higher than control values until by 2 weeks the effect was maximal with mean concentrations of 25 mm for K and 153 mm for Na.4. Ouabain increased the spontaneous salivation rate and ethacrynic acid slowed or prevented it altogether. On the basis of the known sites of action of these drugs it is postulated that two pumps are involved in the regulation of spontaneous salivation. There appears to be basal activity of an acinar mechanism pumping NaCl into the lumen, taking water with it. This pump is activated directly or indirectly by the intracellular Na concentration which itself is controlled by an Na-K exchange pump.5. Excitation of the sympathetic trunk produced a small, though definite, increase in salivation rate. There was evidence that myoepithelial cells might also be involved in the sympathetic response and that they were activated by a receptor stimulation. Salivation evoked by sympathetic nerve stimulation would seem to be a response to , receptor stimulation, but the possibility that activation of both ar and ft receptors was required could not be excluded entirely.

‘Paralytic’ Secretion After Parasympathectomy of Rabbit Submandibular Glands Includes a Cholinergic Component

“…In the 'control' glands the mean value was 0-29 + 0 15 ul min-' gwith a range of 0 18-0-5 #1 min-' g-', which is similar to the results of Smaje (1973) and Gj6rstrup (1977) for normal spontaneous flow.…”

“…The 'spontaneous' flow from the glands that were contralateral to the parasympathetically decentralized glands tended to be greater than that recorded in normal animals (Smaje, 1973;Gj6rstrup, 1977). The explanation for this is not clear but it does indicate that some changes have occurred in the control glands, contralateral to the parasympathectomized ones, and therefore they should not be regarded as truly normal glands.…”

Analysis of reflex responses in preganglionic parasympathetic fibres innervating submandibular glands of rabbits.

“…Calibration was made by injection of a set amount of saline solution into the bottle, and sensitivity of the recording system was determined to measure salivary flow ranging from 0 5 to 100 jf1l. Within this range, however, it was difficult to record a spontaneous secretion, because Smaje (1973) reported that the flow rate of spontaneous secretion was rather slow in submandibular glands ofrabbits, i.e. 0-25 #1l./g.min on average (n = 11).…”

Communications

“…The sweat of children suffering from cystic fibrosis has a raised [Na] which has been shown to be a result of a defect in ductal Na reabsorption (Schulz, 1969). Chronic ligation of the main duct of the rabbit submandibular gland leads to an increase in [Na] in spontaneously secreted saliva (Smaje, 1973) but it is not clear whether this 24P PHYSIOLOGICAL SOCIETY, SEPTEMBER 1978 is also due to deficiency in the ductal Na reabsorptive mechanism. The present experiments were designed to investigate this possibility.…”