FREE-ION CONCENTRATIONS IN RECEPTOR LYMPH AND ROLE OF TRANSEPITHELIALVOLTAGE IN THE FLY LABELLAR TASTE RECEPTOR

Free ion concentrations in the receptor lymph of the labellar taste ha ir were examined on the fleshfly Boettcherisca peregrina, making use o f several kinds of ion-selective microelectrodes inserted into the out er lumen of the taste hair through its cut end. The receptor lymph was rich in Na+ and Cl- but poor in K+, that is, concentrations of Tree N a+, K+, Ca2+ and Cl- were (in mM) 117, 24, 0.2 and 109, respectively. The haemolymph of this insect had similar free ion concentrations. Nex t, the role of transepithelial voltage (TEV; 47.1 +/- 1.0 mV), which t he receptor lymph space of the taste hair had with respect to the haem olymph, was examined. The quantitative relationship between the TEV am plitudes and the impulse frequencies of the sugar receptor evoked by s ucrose stimulation was determined, changing TEV with application of re spiratory inhibitors to the taste hair tip or by injecting current int o the outer lumen. The TEV is concluded to provide the major component of the driving electromotive force for the receptor current to flow.