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Abstract  A gap junction blocker, 18β-glycyrrhetinic acid (β-GA), increased the membrane resistance of Ia, Ib and II/III cells of frog taste disk by 50, 160, and 300 MΩ, respectively, by blocking the gap junction channels and hemichannels. The amplitudes of gustatory depolarizing potentials in the disk cells for 4 basic taste stimuli were reduced to 40–60% after intravenous injection of β-GA at 1.0 mg/kg. β-GA of 1.0 mg/kg did not affect the resting potentials and the reversal potentials for tastant-induced depolarizing potentials in any taste disk cells. The percentage of cells responding to each of 4 basic taste stimuli and varying numbers of 4 taste qualities did not differ between control and β-GA-treated taste disk cells. This implies that gustatory depolarizing response profiles for 4 basic taste stimuli were very similar in control and β-GA-treated taste disk cells. It is concluded that β-GA at 1.0 mg/kg reduced the amplitude of gustatory depolarizing potentials in taste disk cells by strongly blocking depolarizing currents flowing through the gap junction channels and hemichannels, but probably weakly affected the gustatory transduction mechanisms for 4 taste stimuli. [ABSTRACT FROM AUTHOR]

Abstract  Electrical stimulation of parasympathetic nerve (PSN) efferent fibers in the glossopharyngeal nerve induced a slow depolarizing synaptic potential (DSP) in frog taste cells under hypoxia. The objective of this study is to examine the interaction between a gustatory depolarizing receptor potential (GDRP) and a slow DSP. The amplitude of slow DSP added to a tastant-induced GDRP of 10 mV was suppressed to 60% of control slow DSPs for NaCl and acetic acid stimulations, but to 20–30% for quinine–HCl (Q-HCl) and sucrose stimulations. On the other hand, when a GDRP was induced during a prolonged slow DSP, the amplitude of GDRPs induced by 1 M NaCl and 1 M sucrose was suppressed to 50% of controls, but that by 1 mM acetic acid and 10 mM Q-HCl unchanged. It is concluded that the interaction between GDRPs and efferent-induced slow DSPs in frog taste cells under hypoxia derives from the crosstalk between a gustatory receptor current across the receptive membrane and a slow depolarizing synaptic current across the proximal subsynaptic membrane of taste cells. [ABSTRACT FROM AUTHOR]