Transepithelial Potential Changes During Stimulation of Isolated Salivary Glands with 5-Hydroxytryptamine and Cyclic Amp

Abstract
The role of cyclic AMP in mediating the action of 5-HT on salivary glands has been studied by measuring transepithelial potentials. The lumen of unstimulated glands is 4 mV positive but becomes 12 mV negative after treatment with 5-HT (10−8M). Both the potential and the secretory responses to 5-HT are dose-dependent over the same concentration range. The electrical response of salivary glands to cyclic AMP is qualitatively different to that of 5-HT; instead of going negative the potential goes more positive. An increase in positive potential is also observed after treatment with theophylline (10−2M), or when glands are stimulated with 5-HT in a chloride-free saline. These results are consistent with the idea that 5-HT has two actions. One is to stimulate the enzyme adenyl cyclase to synthesize cyclic AMP, which, in turn, stimulates cation transport. The other is to increase anion transport by a mechanism which is independent of cyclic AMP.