title: Depression of gustatory receptor potential in frog taste cell by parasympathetic nerve-induced slow hyperpolarizing potential.
abstract: Parasympathetic nerve (PSN) innervates taste cells of the frog taste disk, and electrical stimulation of PSN elicited a slow hyperpolarizing potential (HP) in taste cells. Here we report that gustatory receptor potentials in frog taste cells are depressed by PSN-induced slow HPs. When PSN was stimulated at 30 Hz during generation of taste cell responses, the large amplitude of depolarizing receptor potential for 1 M NaCl and 1 mM acetic acid was depressed by approximately 40% by slow HPs, but the small amplitude of the depolarizing receptor potential for 10 mM quinine-HCl (Q-HCl) and 1 M sucrose was completely depressed by slow HPs and furthermore changed to the hyperpolarizing direction. The duration of the depolarizing receptor potentials depressed by slow HPs prolonged with increasing period of PSN stimulation. As tastant-induced depolarizing receptor potentials were increased, the amplitude of PSN-induced slow HPs inhibiting the receptor potentials gradually decreased. The mean reversal potentials of the slow HPs were approximately -1 mV under NaCl and acetic acid stimulations, but approximately -14 mV under Q-HCl and sucrose stimulations. This implies that when a slow HP was evoked on the same amplitude of depolarizing receptor potentials, the depression of the NaCl and acetic acid responses in taste cells was larger than that of Q-HCl and sucrose responses. It is concluded that slow HP-induced depression of gustatory depolarizing receptor potentials derives from the interaction between gustatory receptor current and slow hyperpolarizing current in frog taste cells and that the interaction is stronger for NaCl and acetic acid stimulations than for Q-HCl and sucrose stimulations.
authors.affiliation: Division of Integrative Sensory Physiology, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan. toshi@net.nagasaki-u.ac.jp
authors.forename: Toshihide
authors.initials: T
authors.lastname: Sato
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Nishishita
authors.forename: Takao
authors.initials: T
authors.lastname: Mineda
authors.forename: Yukio
authors.initials: Y
authors.lastname: Okada
authors.forename: Kazuo
authors.initials: K
authors.lastname: Toda
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D008564:Membrane Potentials; D010275:Parasympathetic Nervous System / Q000502:physiology*; D011892:Rana catesbeiana; D013650:Taste Buds / Q000502:physiology*