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Saccharin activates cation conductance via inositol 1,4,5‐trisphosphate production in a subset of isolated rod taste cells in the frog
Author(s) -
Okada Yukio,
Fujiyama Rie,
Miyamoto Takenori,
Sato Toshihide
Publication year - 2001
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2001.01391.x
Subject(s) - saccharin , chemistry , biophysics , intracellular , inositol , patch clamp , conductance , endocrinology , medicine , biochemistry , biology , receptor , mathematics , combinatorics
The transduction mechanism of the conductance activated by saccharin was analysed in isolated bullfrog taste cells under whole‐cell voltage‐clamp. Bath application of 30 m m saccharin induced an inward current of −34 ± 12 pA (mean ± SEM, n = 10) at a membrane potential of −50 mV in 10 (23%) of 44 rod cells. The concentration–response relationship for the saccharin‐gated current was consistent with that of the gustatory neural response. The saccharin‐induced current was accompanied with a conductance increase under internal low Cl – condition ( E Cl = −56 mV), suggesting that saccharin activated a cation conductance. The reversal potential of the saccharin‐induced current was −17 ± 2 mV ( n = 10). Intracellular dialysis of 0.5 m m guanosine 5′‐ O ‐(2‐thiodiphosphate) (GDP‐β‐S) completely blocked the saccharin‐induced response, suggesting the involvement of a G protein in the transduction. The dialysis of heparin (1 mg/mL) also inhibited the response almost completely, but the dialysis of 1 m m 8‐Br‐cAMP did not affect the response significantly. Intracellular 50 µ m inositol 1,4,5‐trisphosphate (1,4,5 InsP 3 ) also induced the inward current in five (38%) of 13 rod cells, but intracellular Pasteurella multocida toxin (5 µg/mL, Gαq‐coupled PLC activator) did not elicit any response in the cells. The results suggest that saccharin mainly activates a cation conductance in frog taste cells through the mediation of IP 3 production.