Multiple receptor sites for nucleotide reception in the labellar taste receptor cells of the fleshfly Boettcherisca peregrina

Abstract

Nucleotides applied to the labellar chemosensory hair of the fleshfly, Boettcherisca peregrina, stimulated the taste receptor cells. Adenosine 5′-diphosphate (ADP) evoked a large response of the sugar receptor cell (sugar response) and guanosine 5′-diphosphate (GDP) evoked a large response of the salt receptor cell (salt response), but the salt response to ADP and the sugar response to GDP were relatively small. While the sugar response to ADP was independent over a wide range, pH 5–9, the salt responses to GDP and ADP were inhibited at neutral and alkaline pH's, even though they elicited a marked salt response between pH's of about 5 and 6. Only adenine nucleotides (ADP, AMP, ATP) could stimulate the sugar receptor cell, with an order of stimulating effectiveness of ADP>>AMP≥ATP. However, the salt receptor cell could respond significantly not only to GDP but various nucleoside 5′-diphosphates, nucleoside 5′-monophosphates, cyclic nucleotides and thiamine diphosphate. These results clearly suggest that the specificity of the receptor site reacting with nucleotide in the sugar receptor cell is very different from that in the salt receptor cell.