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Fig. 6. Effects of agonists and antagonists for various GABA receptor subtypes on
the membrane potential (Vm) changes evoked by salivary
duct nerve (SDN)-stimulation. Asterisks mark the timepoints of stimulation (5
V, 0.2 ms, 5 Hz, 2 s trains). The duration of drug application is indicated by
bars. (A,B) Application of SKF97541 or baclofen mimic the GABA-induced
enhancement in the electrical responses. (C,D) CGP52432 and CGP54626 suppress
the GABA-induced enhancement. (E) The GABABR antagonist CGP52432
suppresses the SKF97541-induced enhancement. (F) Bicuculline-induced
augmentation of electrical responses of acinar cells to SDN-stimulation. (G)
Bar chart for the effects of all tested drugs. The gray dotted line indicates
the control amplitude (=100%) induced by electrical SDN-stimulation in the
absence of GABA and other drugs. The number of replicates for each bar is
stated in parentheses. The bars show means±s.e.m. Muscimol
(GABAAR agonist), picrotoxin (GABAAR antagonist), THIP
(GABACR antagonist and partial GABAAR agonist) and TPMPA
(GABACR antagonist) did not affect the control amplitudes or the
GABA-induced enhancement. The GABABR-specific agonists SKF97541 and
baclofen enhanced the acinar cell response amplitudes. The GABABR
antagonists CGP54626 and CGP52432 suppressed the GABA-induced enhancement.
Bicuculline also enhanced the cell responses to SDN-stimulation. The mean
amplitude of at least two stimulations during GABA-bath application and/or
drug treatment was normalized to the mean amplitude of at least two
consecutive control stimulations for each experiment. The data were analyzed
by applying one-way analysis of variance and Tukey's post test.
*P<0.05, **P<0.001.
