The effects of 5-hydroxytryptamine and cyclic AMP on the potential profile across isolated salivary glands

The sites of the transepithelial potential changes produced by 5-HT and cyclic AMP in the salivary gland of the blowfly (Calliphora) have been investigated. Microelectrodes recorded a two-step potential profile across this epithelium. The cell was negative to both the bathing medium and the saliva. The basal membrane potential was 44·0 ± 0·2 mV and was affected very little by application of either 5-HT or cyclic AMP. The apical membrane was depolarized by 5-HT and in contrast was hyperpolarized by cyclic AMP. On the basis of these results it is concluded that 5-HT has two actions: (a) to stimulate a potassium pump on the apical membrane using cyclic AMP as an intermediary, (b) to increase chloride movement by a mechanism not directly involving cyclic AMP.