Inositol 1,4,5-trisphosphate transduction cascade in taste reception of the fleshfly, Boettcherisca peregrina

The role of an inositol 1,4,5-trisphosphate (IP₃)-mediated transduction cascade in the response of taste receptor cells of the fleshfly Boettcherisca peregrina was investigated by using the following reagents: neomycin (an inhibitor of IP₃ production), U73122 (an inhibitor of phospholipase C), adenophostin A (an agonist of the IP₃-gated channel), IP₃, ruthenium red (a blocker of the IP₃-gated channel), and 2-aminoe-thoxydiphenylborate (2-APB; an antagonist of the IP₃-gated channel). For introduction into the receptor cell, the reagents were mixed with a detergent, deoxycholate (DOC). After treatment with neomycin + DOC or U73122 + DOC, the response of the sugar receptor cell to sugars was depressed compared with responses after treatment with DOC alone. During the treatment of adenophostin A + DOC, the response of the sugar receptor cell was elicited. After treatment with IP₃ + DOC, the response of the sugar receptor cell to sugars and to amino acids was apparently enhanced. When taste stimuli were administered in the presence of ruthenium red or 2-APB, the response of the sugar receptor cell to glucose were inhibited. The expression of genes for substances involved in the IP₃ transduction cascade, such as G protein α subunit (dGqα), phospholipase C (norpA), and IP₃ receptor (itpr), were examined in the taste receptor cell of the fruitfly Drosophila melanogaster by using the pox-neuro⁷⁰ mutant (poxn⁷⁰), which lacks taste receptor cells. The expressed levels of dGqα and itpr in the tarsus of poxn⁷⁰ mutant flies were reduced compared with those of wild-type flies. These results suggest that the IP₃ transduction cascade is involved in the response of the sugar receptor cell of the fly.