The Effects of 5-Hydroxytryptamine and Cyclic Amp on the Potential Profile across Isolated Salivary Glands

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Abstract
1. 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. 2. Microelectrodes recorded a two-step potential profile across this epithelium. The cell was negative to both the bathing medium and the saliva. 3. The basal membrane potential was 44·0±0·2 mV and was affected very little by application of either 5-HT or cyclic AMP. 4. The apical membrane was depolarized by 5-HT and in contrast was hyperpolarized by cyclic AMP. 5. 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.