Abstract:
The effect of calcium-sensing receptor (CaR) agonists on frog gustatory
responses was studied using glossopharyngeal nerve recording and whole-cell patch clamp recording of isolated taste disc cells. Calcimimetic NPS R-467 dissolved in normal
saline solution elicited a large transient response in the nerve. The less active enantiomer
of the compound, NPS S-467 induced only a small neural response. The EC50 for NPS R 467 was about 20 lM. Cross-adaptation experiments were performed to examine the
effect of 30 lM NPS R-467 and 100 lM quinine on the gustatory neural response. The
magnitude of the R-467-induced response after adaptation to quinine was approximately
equal to that after adaptation to normal saline solution, indicating that the receptor site
for NPS R-467 is different from the site for quinine. NPS R-467 (100 lM) also induced an
inward current accompanied with conductance increase and large depolarization in two
(13%) of 15 rod cells, and a sustained decrease in outward current and small
depolarization in six (40%) other rod cells. NPS S-467 (100 lM) induced a sustained
decrease in outward current and depolarization in five (50%) of 10 rod cells. Another
calcimimetic cinacalcet (100 lM) induced an inward current accompanied with conduc tance increase in three (27%) of 11 rod cells. The results suggest that NPS R-467 induces
neural responses through cell responses unrelated to a resting K+ conductance decrease.
