Secretory effects of 5‐hydroxytryptamine following neonatal sympathectomy in rat parotid gland

Abstract

Unilateral sympathetic denervation of rat parotid glands was performed within 4 h after birth. Nine weeks later the glands were used for in-vitro studies of amylase secretion, and 86Rb+ was used as a marker for potassium efflux. The non-denervated contralateral glands served as controls. The tissue concentrations of 5-hydroxytryptamine and its metabolite 5-hydroxyindole acetic acid were also measured. 5-Hydroxytryptamine caused a significant dose-dependent increase in amylase secretion, which was inhibited by methysergide. There was no difference between controls and denervated glands. 5-Hydroxytryptamine was without effect on potassium efflux from either denervated or control glands. The sympathectomy caused increased levels of 5-hydroxytryptamine and 5-hydroxyindole acetic acid as compared with contralateral controls. The results suggest that 5-hydroxytryptamine influences the two main secretory processes in rat parotid gland differently. A significant amylase discharge was seen following 5-hydroxytryptamine stimulation, whereas no effect was seen on 86Rb+ efflux. Although it is also proposed that there are no 5-hydroxytryptamine-associated nerves in the superior cervical ganglion innervating parotid tissue, it seems that there is a complex connection between the sympathetic pathway and the serotoninergic system.

Intraluminal volume homeostasis

“…Analogously, rat parotid salivary glands show opposing effect of 5-HT on secretion of saliva and enzyme amylase. 19,22,23 5-HT treatment decreases salivary flow rate but increased amylase secretion. This might be due to action via specific 5-HT receptor subsets which need to be experimentally tested in the parotid gland.…”

“…In perfused rat submaxillary glands, 5-HT decreased the saliva flow rate initiated by acetylecholine (Ach). 19,22,23 Analysis in the dispersed cell aggregates from the gland showed cAMP accumulation in response to 5-HT suggesting a receptor-mediated action of 5-HT in regulating saliva volume and protein content. 19,22,23 Similar cAMP accumulation in response to 5-HT was observed in mouse and opossum submaxillary glands and rat sublingual and parotid glands.…”

Modulation by thyroid hormones of rat parotid amylase secretion stimulated by 5‐hydroxytryptamine

“…5‐Hydroxytryptamine regulates salivary gland secretion from invertebrates such as snails (24), cockroaches (3), blowflies (25), and mosquitoes (26), increasing the salivary flow rates and the concentration of proteins. In rodents, 5‐HT induces amylase secretion from parotid and submandibular glands (7, 8), probably by the cAMP pathway, which represents the main pathway involved in the salivary amylase secretion (27). This is in consonance with the recently reported presence of 5‐HT 4b and 5‐HT 7a receptors in the rat submandibular gland (9), both receptor subtypes being coupled to the cAMP pathway (28).…”

“…Although the salivary gland's response to 5‐HT has been extensively studied in insects (2–4), there are few papers on submandibular and parotid secretion in mammals in response to 5‐HT. The salivary glands of mammals respond to the administration of 5‐HT by changes in salivary flow rate (5), protein secretion (6), amylase secretion (7, 8), and cyclic AMP (cAMP) production (9). Furthermore, it has been reported that rat parotid gland presents basal 5‐HT amounts similar to basal acetylcholine levels (10).…”

Serum amylase in bulimia nervosa: Clinical status and pathophysiology

“…Alpha adrenergic stimuli appear to cause contraction of the myoepithelial cells and thus increase salivary flow and intraductal pressures (Procter et al, 1989). Other neurotransmitters that have been shown to have effect in animal studies of parotid gland tissue are dopamine, serotonin (5-HT), and substance P (Dannielsson, Henriksson, Sundstrom, & Wester, 1988;Henriksson, Sundstrom, Danielsson, & Hellstrom, 1990;Liang & Cascieri, 1979).…”