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Some characteristics of the functioning of membrane receptor‐channel complexes of Limnaea stagnalis neurones.
Author(s) -
Panarin V A,
Kondratyev V A,
Rayevsky O A
Publication year - 1990
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1990.sp018027
Subject(s) - acetylcholine , conductance , chemistry , membrane potential , biophysics , membrane , acetylcholine receptor , membrane channel , analytical chemistry (journal) , receptor , endocrinology , physics , biochemistry , biology , chromatography , condensed matter physics
1. Limnaea stagnalis neurones have been used to study the functioning of membrane receptor‐channel complexes. The experiments were performed using a fixed membrane potential (E) and the intracellular perfusion technique. The cells employed responded to acetylcholine (ACh) by changing only their Cl‐ conductance. 2. ACh‐induced currents, their fluctuations and relaxations resulting from a jump of E were studied. 3. The following facts have been established based on analysis of ACh currents, their fluctuations and relaxations: (1) the characteristic time of the exponential decay of the autocorrelation function, tau N, is in the range of 15‐20 ms; (2) the characteristic relaxation time, tau R, equals 50‐60 ms (ACh concentration = 0.25 microM, desensitization is not observed); (3) E does not exert any functionally significant effect upon tau N or tau R which could have governed the non‐linearity of the membrane voltage‐current characteristic; (4) variation of ACh concentration from 0.25 to 1 microM has a significant effect on tau R but not on tau N; (5) lowering of the ACh solution temperature from 22 to 8.5 degrees C results in a 20% increase of the ACh current, a 3‐ to 4‐fold decrease of the single‐channel conductance (gamma), a 20% increase in tau N and a 3‐ to 4‐fold increase in tau R. 4. The suberylcholine (SCh)‐induced membrane current has approximately the same value as the ACh‐induced current at equal concentrations of ACh and SCh (0.25 microM); the tau N and gamma values were also quite close, but tau R was 2.3 times lower for SCh than for ACh. 5. An essentially two‐stage scheme of functioning of membrane receptor‐channel complexes is proposed. The scheme has two distinguishable and measurable stages and involves five closed states and one open state; it offers an explanation for our experimental data as well as the results of other workers.