title: A calcium-receptor agonist induces gustatory neural responses in bullfrogs.
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 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.
authors.affiliation: Integrative Sensory Physiology, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki, Nagasaki 852-8588, Japan. okada@nagasaki-u.ac.jp
authors.forename: Yukio
authors.initials: Y
authors.lastname: Okada
authors.forename: Kotapola G
authors.initials: KG
authors.lastname: Imendra
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Hotokezaka
authors.forename: Rie
authors.initials: R
authors.lastname: Fujiyama
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Zeredo
authors.forename: Kazuo
authors.initials: K
authors.lastname: Toda
mesh_terms: 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*
chemical_list: D000814:Aniline Compounds; C111654:NPS R-467; D009281:Naphthalenes; D044169:Receptors, Calcium-Sensing; D012965:Sodium Chloride; D000069449:Cinacalcet