Thus, while the effect of 5b on the inward currents reebok look could be explained by the direct involvement of ASICs in PSC generation as observed in the amygdala [ 5 ], the lack of an increase of the outward currents suggests that the effect of 5b is predominantly modulatory. Lack of apparent shift of estimated PSCs reversal potential (-0.75 ± 0.26 mV, n = 8) after application of 5b also supports this suggestion. (see Methods for details of estimating PSCs reversal potential). Nevertheless, to further verify this point we tried to pharmacologically isolate/enhance a fraction of synaptic current that is not mediated by GABA A -receptors (residual current) and study some of its properties.
In spite of growing evidence indicating that the density of reebok classic ASICs is substantially higher in GABAergic interneurons than in glutamatergic cells [ 17 ] and recent demonstration of functional crosstalk between ASICs and GABA A -receptors [ 10 , 11 ], the possible involvement of ASICs in the regulation of GABAergic reebok shoes transmission remained unclear. In our work we present evidence for the first time that ASICs play a functional role at hippocampal GABAergic synapses. This role is mediated, at least partially, by a postsynaptic but (predominantly) modulatory mechanism.We found that GABAergic postsynaptic currents, recorded below their reversal potential as inward currents, are suppressed by all the employed blockers of ASICs.
In the same cells the suppression of postsynaptic currents, recorded above their reversal potential as outward currents was statistically insignificant.Apart from the chemical reebok the pump dissimilarity of amiloride and diminazene, they are structurally different [ 24 ], and mechanisms of their action on ASICs are different as well [ 24 ]. Similarly, amiloride and 5b have different mechanisms of action on ASICs [ 21 ]. Indeed, 5b is an orthosteric antagonist of ASIC1 [ 21 ] while amiloride is an open channel blocker [ 33 ].
Activation of GABA A -receptors strongly changed ASIC-currents amplitude and pharmacological sensitivity [ 10 ], and the effect was blocked by antagonists of GABA A receptors [ 10 ]. On the other hand, a modulatory effect of ASIC activation on GABA A -currents was also observed in HEK293 cells co-transfected with GABA A and ASIC1a or in primary cultured DRG neurons. The immunoassays showed that both GABA A and ASIC1a proteins were co-immunoprecipitated mutually either in HEK293 cells co-transfected with GABA A and ASIC1a or in reebok pump primary cultured DRG neurons [ 11 ]. These data suggest direct protein-protein mechanism of interaction between GABA A and ASICs.
This suggestion is also indirectly supported by the observation that modulatory effect of GABA A -receptors activation on ASICs-currents can be observed in excised patches [ 10 ]. We assume that an interaction between ASICs and GABA A -receptors is quite likely to occur at GABAergic synapses upon acidification at the synaptic cleft. This assumption can be supported by the lack of the apparent effect of 5b on inward PSCS in the presence of bicuculline, observed in our experiments.