A calcium-receptor agonist induces gustatory neural responses in bullfrogs.
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 EC(50) for NPS R-467 was about 20 microM. Cross-adaptation experiments were performed to examine the effect of 30 microM NPS R-467 and 100 microM 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 microM) 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 microM) induced a sustained decrease in outward current and depolarization in five (50%) of 10 rod cells. Another calcimimetic cinacalcet (100 microM) induced an inward current accompanied with conductance 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.
Okada
Yukio
Y
Integrative Sensory Physiology, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki, Nagasaki 852-8588, Japan. okada@nagasaki-u.ac.jp
Imendra
Kotapola G
KG
Miyazaki
Toshihiro
T
Hotokezaka
Hitoshi
H
Fujiyama
Rie
R
Zeredo
Jorge L
JL
Toda
Kazuo
K
D000814:Aniline Compounds / Q000494:pharmacology*; D000818:Animals; D000069449:Cinacalcet; D005930:Glossopharyngeal Nerve / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009281:Naphthalenes / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011892:Rana catesbeiana / Q000502:physiology*; D044169:Receptors, Calcium-Sensing / Q000819:agonists*; D012965:Sodium Chloride / Q000494:pharmacology; D013650:Taste Buds / Q000187:drug effects*
D000814:Aniline Compounds; C111654:NPS R-467; D009281:Naphthalenes; D044169:Receptors, Calcium-Sensing; D012965:Sodium Chloride; D000069449:Cinacalcet