Tetraethylammonium ions and the potassium permeability of excitable cells

Stanfield, Peter

doi:10.1007/bfb0035345

Cited by 228 publications

(126 citation statements)

References 329 publications

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“…Effects of TEA or Ba2+ on the muscarinic current Extracellular TEA has been found to suppress not only voltage-gated K+ channels (reviewed by Stanfield, 1983) but also the nicotinic cation channel at the frog endplate (TEA used at around 0-1 mM; Adler, Oliveira, Albuquerque, Mansoure & Eldefrawi, 1979). TEA (0-03-3 mM) was added to the standard bath solution, and the response to 1 /LM-oxotremorine was studied.…”

Section: Resultsmentioning

confidence: 99%

Muscarinic receptor is coupled with a cation channel through a GTP‐binding protein in guinea‐pig chromaffin cells.

Inoue

Kuriyama

1991

The Journal of Physiology

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SUMMARY1. The ionic current evoked by muscarinic receptor agonists was investigated in dispersed chromaffin cells of the guinea-pig adrenal medulla using the whole-cell version of the patch-clamp procedure.2. Muscarine or oxotremorine (0-03-10 #M) produced an inward current associated with an increase in current noise at a holding potential of -40 mV. The relationship between current and oxotremorine concentration fitted well to a rectangular hyperbole with an apparent dissociation constant (KA) of 0-23 JiM.3. The muscarinic antagonists pirenzepine (0-1 ftM) and AF-DX 116 (0 3 /LM) shifted the dose-response curve to the right in a parallel manner. Dissociation constants (KB) for pirenzepine and AF-DX 116 were estimated to be 50 and 70 nm, respectively.4. The current-voltage relation for the current induced by muscarine had a negative slope below -30 or -20 mV, and the current reversed its polarity at 0-4 + 0-8 mV (n = 4) in standard salt solution. Removal of Mg2+ or Ca2+ from the perfusate did not modify the muscarinic current-voltage relationship.5. When Na+ in the bath solution was replaced with Tris, the muscarinic current-voltage relationship shifted to the left (the hyperpolarizing direction); the current reversed its polarity at -18-7 + 1-2 mV in a solution containing 72 mM-Na+ (three cells) and at -57-5 + 2-7 mV in nominally Na+-free solution (three cells). When Ca21 was replaced by Mg2+, in Na+-free solution, an inward current was not evoked by muscarinic stimulation.6. Tetraethylammonium (TEA; 0-03-3 mM) reduced the muscarinic current at -40 mV, and the KD value was 0-34 mm with a Hill coefficient of 1. Barium (4 mM) reduced the current to 0-69 + 0-06 of control (n = 3).7. When the recording electrodes contained guanosine-5'-O-(3-thiophosphate) (GTPyS, 100 UM), an inward current developed at -55 mV during the first few minutes after breaking into the cell interior. This inward current was associated with

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Section: Resultsmentioning

confidence: 99%

Muscarinic receptor is coupled with a cation channel through a GTP‐binding protein in guinea‐pig chromaffin cells.

Inoue

Kuriyama

1991

The Journal of Physiology

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“…Effects of TEA and quinine TEA and quinine (or its stereoisomer quinidine) have been shown to block the Ca-induced hump of K currents in several preparations: for review of TEA effects see Stanfield (1983); Hermann & Gorman (1984). In chromaffin cells, both drugs reversibly block single-channel currents through BK channels (A. Marty, unpublished observations).…”

Section: K+ Channels In Chromaffin Cellsmentioning

confidence: 99%

Potassium channels in cultured bovine adrenal chromaffin cells.

Marty¹,

Neher

1985

The Journal of Physiology

305

215

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SUMMARY1. K channels of bovine adrenal chromaffin cells were studied using patch-clamp techniques.2. Whole-cell K currents measured near + 10 mV were much larger in 1 mM-external Ca than in Ca-free saline. Noise analysis suggested that this Ca-dependent current was carried by a large unitary conductance channel, called BK channel, which was previously described in inside-out patches (Marty, 1981).3. The Ca-dependent K current near + 10 mV declined with time due to 'run-down' of Ca channels. At the same time, a fraction of the outward current observed above + 50 mV was also eliminated. This outward current component probably represents K efflux through Ca channels.4. Whole-cell Ca-dependent K currents were studied using various Ca buffers.EGTA buffers were surprisingly inefficient: in order to block the current entirely, it was necessary to use an isotonic EGTA solution and to increase internal pH. 1 ,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) was at least five times more efficient than EGTA.5. In isolated patches three types of single-channel K currents were observed. Under normal ionic conditions (140 mM-K inside, 140 mM-Na outside), the unitary conductances measured between -20 and +40 mV were 96 pS, 18 pS and 8 pS. The 96 pS channels are the Ca-dependent BK channels.6. 18 pS and 8 pS channels were both activated and then inactivated by membrane depolarization. Both displayed complex kinetics; single-channel currents were grouped in bursts. Activation and inactivation kinetics were faster for the 18 pS channel (therefore termed FK channel, for fast K channel) than for the 8 pS channel (SK channel, for slow or small amplitude channel). The voltage dependence ofopening probability was steeper for the FK channel as compared to the SK channel.

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“…The Goldman-Hodgkin-Katz equation gives a ratio of Cl − to Na + permeability (P Cl :P Na ) of 5.9 for MSL10. We also measured the conductance of MSL10 when Na + was replaced with TEA + , a large ion with an estimated diameter of 8 Å (23) often used as a pore blocker of potassium channels (24,25). Because Hille's equation (26) also predicts an approximate pore diameter of 8 Å for MSL10 (assuming the pore to be a uniform cylinder 5 nm in length), TEA + is not likely to permeate the MSL10 channel pore, nor does TEA + serve to block MSL10 (Fig.…”

Section: Msl10 Exhibits a Moderate Preference For Anionsmentioning

confidence: 99%

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions

Maksaev

Haswell

2012

Proc. Natl. Acad. Sci. U.S.A.

132

156

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Like many other organisms, plants are capable of sensing and responding to mechanical stimuli such as touch, osmotic pressure, and gravity. One mechanism for the perception of force is the activation of mechanosensitive (or stretch-activated) ion channels, and a number of mechanosensitive channel activities have been described in plant membranes. Based on their homology to the bacterial mechanosensitive channel MscS, the 10 MscS-Like (MSL) proteins of Arabidopsis thaliana have been hypothesized to form mechanosensitive channels in plant cell and organelle membranes. However, definitive proof that MSLs form mechanosensitive channels has been lacking. Here we used single-channel patch clamp electrophysiology to show that MSL10 is capable of providing a MS channel activity when heterologously expressed in Xenopus laevis oocytes. This channel had a conductance of ∼100 pS, consistent with the hypothesis that it underlies an activity previously observed in the plasma membrane of plant root cells. We found that MSL10 formed a channel with a moderate preference for anions, which was modulated by strongly positive and negative membrane potentials, and was reversibly inhibited by gadolinium, a known inhibitor of mechanosensitive channels. MSL10 demonstrated asymmetric activation/ inactivation kinetics, with the channel closing at substantially lower tensions than channel opening. The electrophysiological characterization of MSL10 reported here provides insight into the evolution of structure and function of this important family of proteins.T he perception of mechanical stimuli like gravity, touch, or osmotic pressure is essential to normal plant growth and development and is further implicated in biotic and abiotic stress responses (1). One of the best-studied strategies for perceiving force involves membrane-embedded channels that are gated by tension, known as mechanosensitive (MS) channels (2). Numerous MS channel activities (>17 to date) have been described in the membranes of diverse tissues from a variety of plant species (summarized in ref. 3, also refs. 4 and 5). Many of these observed MS channel activities differ in their conductance, ion selectivity, and/or sensitivity to the direction of activation pressure, suggesting that multiple classes of mechanosensitive channels are present in plant cells.No mechanosensitive ion channel activity discovered in plant membranes has yet been definitively identified at the molecular level, but two families of proteins serve as strong candidates. The first is the Mid1-Complementing Activity (MCA) family, members of which are required for root response to touch in the model plant Arabidopsis thaliana, induce Ca 2+ uptake in rice and Arabidopsis cells (6, 7), and are associated with increased current in response to hypotonic stimulation of Xenopus oocytes (8). The second family of candidates for plant MS channels is the MscS-Like (MSL) family, first identified based on modest homology to the wellcharacterized bacterial MS channel MscS from Escherichia coli (3, 9). MscS is a lar...

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Tetraethylammonium ions and the potassium permeability of excitable cells

Cited by 228 publications

References 329 publications

Muscarinic receptor is coupled with a cation channel through a GTP‐binding protein in guinea‐pig chromaffin cells.

Muscarinic receptor is coupled with a cation channel through a GTP‐binding protein in guinea‐pig chromaffin cells.

Potassium channels in cultured bovine adrenal chromaffin cells.

MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions

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