SUGAR SENSITIVITY OF A LABELLAR SALT RECEPTOR OF THE BLOWFLY PROTOPHORMIA-TERRAENOVAE

The salt receptor of the "largest" labellar hairs in the blowfly responds to stimulation by sugars. Electrophysiological investigations using the tip recording technique gave the following results: 1. (1) Addition of 100 mM sucrose to 10 mM sodium chloride leads to an increase of the spike activity of the salt receptor by factors around 2-6. 2. (2) d-glucose, sucrose and trehalose that are supposed to bind to the "pyranose" site of the sugar receptor elicit a higher response of the salt receptor than d-fructose which binds to the "furanose' site. 3. (3) l-fucose has a stronger stimulatory effect than its enantiomer d-fucose, confirming the assumption of stereospecific interactions between sugars and the salt receptor. The data strongly suggest the existence of at least one sugar-specific site in the dendritic membrane of the classic "salt" receptor. This site resembles the "pyranose" site of the sugar receptor. The biological meaning of our results is discussed. A precondition for the analysis was a computer-aided improvement of the spike identification in multicellular responses. © 1990.