The inhibitory chloride channel activated by glutamate as well as γ-amino-butyric acid (GABA).

Autor: Franke, Ch., Hatt, H., Dudel, J.
Zdroj: Journal of Comparative Physiology A: Sensory, Neural & Behavioral Physiology; Nov1986, Vol. 159 Issue 5, p591-609, 19p
Abstrakt: Outside-out and inside-out patches of membrane were excised from different muscles of crayfish ( Austropotamobius torrentium) and single channel currents elicited by synaptic transmitters and their analogues were measured with the patchclamp technique. If the Cl-concentration was high on both sides of the membrane, glutamate even at concentrations <1 μ M elicited low amplitude single channel currents, which were identified to be Cl-currents. The same channels were also activated by 10 μ M GABA. Glutamate and GABA showed competition in activating these inhibitory channels. Amplitude histograms of the single channel currents presented well defined peaks corresponding to 3 channel substates I, I and I, with conductances of about γ(I)=22 pS in high chloride corresponding to a permeability π(I)=3.5× 10 cm/s), γ(I)=2 γ(I) and γ(I)=3 γ(I). Glutamate activated preferably state I, and GABA state I, but both could activate all states at sufficient concentration. Distributions of the open times in the different states were plotted and could be fitted each with one or two exponentials described by time constants of τ(I) of 1 and 6 ms, τ(I) of 2 to 3 ms, and τ(I) or 1 to 2 ms. The burst durations had components of 3 to 4 and of 30 to 40 ms. All these durations were approximately the same when the channels were activated by glutamate and GABA. The analogue quisqualate of glutamate, as well as the GABA analogue β-guanidino propionic acid also elicited the respective patterns of states of the inhibitory channel. Quisqualate is by far the most effective agonist and glutamate is more effective than GABA at the inhibitory receptor. Picrotoxin blocked activation of the inhibitory channel by GABA more effectively than by glutamate. The importance of the activation of the inhibitory channel by glutamate as well as by GABA and their analogues is discussed. Elements of a tentative reaction schema are proposed. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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