Reaction spectra of sugar receptors in different taste hairs of the fly
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- Wieczorek, H. & Köppl, R. J. Comp. Physiol. (1982) 149: 207. doi:10.1007/BF00619214
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The reaction spectra of sugar receptors, based on the maximal receptor responses to a set of sixteen sugars, are equal in five different types of labellar taste hairs for sugars binding to the pyranose site. D-fructose which reacts on the furanose site, as well as the aryl glucosides 4-nitrophenyl-α-glucoside and phenyl-α-glucoside exert different stimulating effects in sugar receptors of different hair types.
Mixtures of 4-nitrophenyl-α-glucoside with 1 mol/1 D-glucose and with 1 mol/1 D-fucose elicit 20 % enhanced responses in sugar receptors of the “large” labellar hairs, although D-glucose as well as D-fucose, if applied alone, induce maximal receptor responses.
Sugar receptors of different tarsal taste hairs differ strikingly in their sensitivities to 4-nitrophenyl-α-glucoside which is a strong stimulus in “D”-type hairs, while it has almost no stimulating effectiveness in “B”-hairs.
It is suggested that 4-nitrophenyl-α-glucoside, one of the most effective stimuli for the sugar receptors of the fly, binds neither to the pyranose nor to the furanose site of the sugar receptor; probably it reacts on a new, hitherto unidentified receptor site. Evidences are discussed that the sugar sensitive labellar receptor cells of the fly may be a favourable object for the study of coding problems.