Matching molecules to function: neuronal Ca2+-activated K+ channels and afterhyperpolarizations

Stocker, Martin; Hirzel, Klaus; D’hoedt, Dieter; Pedarzani, Paola

doi:10.1016/j.toxicon.2003.12.009

Cited by 74 publications

(57 citation statements)

References 198 publications

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“…The effects of either apamin or ScTX were difficult to reverse, possibly because of their high binding affinities (Stocker et al, 2004). At the same time, there can be little question as to the specific action of these agents because they produced unique, positive effects.…”

Section: Presynaptic Components In Bt/bm Afferentsmentioning

confidence: 99%

Mechanisms of Efferent-Mediated Responses in the Turtle Posterior Crista

2006

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Section: Presynaptic Components In Bt/bm Afferentsmentioning

confidence: 99%

Mechanisms of Efferent-Mediated Responses in the Turtle Posterior Crista

2006

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“…In particular, 100 M DCEBIO increased the amplitude of the SK-mediated I AHP by 195 Ϯ 40% and prolonged its duration by 319 Ϯ 42%. sI AHP co-exists with I AHP in CA1 pyramidal neurons but is mediated by channels clearly distinct from the SK channels underlying I AHP and of as yet unknown molecular identity (2)(3)(4)(5)9). Neither the sI AHP amplitude (118 Ϯ 10%) nor its time constant of decay (112 Ϯ 5%) were significantly increased by DCEBIO (Fig.…”

Section: Dcebio and Ns309 Sk Channel Enhancers More Potent Than 1-ebmentioning

confidence: 99%

“…In hippocampal pyramidal neurons voltage-independent, Ca 2ϩ -activated K ϩ channels are responsible for the generation of two distinct afterhyperpolarizing currents, I AHP 5 and sI AHP (1)(2)(3)(4). I AHP is characterized by a time constant of decay of ϳ100 ms and by its sensitivity to the bee venom toxin, apamin, and to the scorpion toxins, scyllatoxin and tamapin (5)(6)(7).…”

mentioning

confidence: 99%

“…I AHP is characterized by a time constant of decay of ϳ100 ms and by its sensitivity to the bee venom toxin, apamin, and to the scorpion toxins, scyllatoxin and tamapin (5)(6)(7). sI AHP is characterized by a slower time course (in the range of seconds), by its lack of sensitivity to apamin or any other classical K ϩ channel blocker, and by its modulation by several neurotransmitters (1)(2)(3)8). Based on their kinetic and pharmacological features and on the results obtained from genetically manipulated mice, SK channels mediate I AHP , whereas the molecular correlate for sI AHP is still unknown (2-4, 9, 10).…”

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confidence: 99%

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Specific Enhancement of SK Channel Activity Selectively Potentiates the Afterhyperpolarizing Current IAHP and Modulates the Firing Properties of Hippocampal Pyramidal Neurons

Pedarzani

McCutcheon

Rogge

et al. 2005

Journal of Biological Chemistry

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138

137

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SK channels are Ca2؉ -activated K ؉ channels that underlie after hyperpolarizing (AHP) currents and contribute to the shaping of the firing patterns and regulation of Ca 2؉ influx in a variety of neurons. The elucidation of SK channel function has recently benefited from the discovery of SK channel enhancers, the prototype of which is 1-EBIO. 1-EBIO exerts profound effects on neuronal excitability but displays a low potency and limited selectivity. This study reports the effects of DCEBIO, an intermediate conductance Ca 2؉ -activated K ؉ channel modulator, and the effects of the recently identified potent SK channel enhancer NS309 on recombinant SK2 channels, neuronal apamin-sensitive AHP currents, and the excitability of CA1 neurons. NS309 and DCEBIO increased the amplitude and duration of the apamin-sensitive afterhyperpolarizing current without affecting the slow afterhyperpolarizing current in contrast to 1-EBIO. The potentiation by DCEBIO and NS309 was reversed by SK channel blockers. In current clamp experiments, NS309 enhanced the medium afterhyperpolarization (but not the slow afterhyperpolarization sAHP) and profoundly affected excitability by facilitating spike frequency adaptation in a frequency-independent manner. The potent and specific effect of NS309 on the excitability of CA1 pyramidal neurons makes this compound an ideal tool to assess the role of SK channels as possible targets for the treatment of disorders linked to neuronal hyperexcitability.In hippocampal pyramidal neurons voltage-independent, Ca 2ϩ -activated K ϩ channels are responsible for the generation of two distinct afterhyperpolarizing currents, I AHP 5 and sI AHP (1-4). I AHP is characterized by a time constant of decay of ϳ100 ms and by its sensitivity to the bee venom toxin, apamin, and to the scorpion toxins, scyllatoxin and tamapin (5-7). sI AHP is characterized by a slower time course (in the range of seconds), by its lack of sensitivity to apamin or any other classical K ϩ channel blocker, and by its modulation by several neurotransmitters (1-3, 8). Based on their kinetic and pharmacological features and on the results obtained from genetically manipulated mice, SK channels mediate I AHP , whereas the molecular correlate for sI AHP is still unknown (2-4, 9, 10). In addition to the use of selective blockers, an important contribution to the elucidation of the physiological role of SK and IK channels has arisen from the use of a small organic compound that enhances channel activity, the benzimidazolinone 1-EBIO (11-15). 1-EBIO enhances the activity of SK channels in the presence of the physiological activator, intracellular Ca 2ϩ , by increasing the apparent sensitivity of SK channels to Ca 2ϩ (14). As a consequence, 1-EBIO increases the amplitude of SK-mediated AHP currents and their duration in a variety of neurons, leading to profound changes in neuronal activity and firing patterns (14, 16 -18). Although 1-EBIO has been a useful tool to elucidate the function of SK channels in their native context, it has some important li...

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“…-channel (VDCC) activity via membrane hyperpolarization (3,4). Agents that activate K Ca may, therefore, cover or enhance this negative feedback mechanism under some of pathophysiological conditions in excitable cells (5).…”

Section: +mentioning

confidence: 99%

Voltage-Dependent Ca2+-Channel Block by Openers of Intermediate and Small Conductance Ca2+-Activated K+ Channels in Urinary Bladder Smooth Muscle Cells

et al. 2006

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Abstract. We examined effects of small and intermediate conductance Ca2+ -activated K + (SK and IK) channel openers, DCEBIO (5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) and NS309 (3-oxime-6,7-dichloro-1H-indole-2,3-dione), on L-type Ca 2+ channel current (I Ca ) that was measured in smooth muscle cells isolated from mouse urinary bladder under whole cell voltage-clamp. The I Ca was concentration-dependently inhibited by DCEBIO and NS309; half inhibition was obtained at 71.6 and 10.6 µM, respectively. The specificity of NS309 to the IK channel over the Ca 2+ channel appears to be high and higher than that of DCEBIO. DCEBIO and even NS309 may, however, substantially block Ca 2+ channels when used as SK channel openers.

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Matching molecules to function: neuronal Ca2+-activated K+ channels and afterhyperpolarizations

Cited by 74 publications

References 198 publications

Mechanisms of Efferent-Mediated Responses in the Turtle Posterior Crista

Mechanisms of Efferent-Mediated Responses in the Turtle Posterior Crista

Specific Enhancement of SK Channel Activity Selectively Potentiates the Afterhyperpolarizing Current IAHP and Modulates the Firing Properties of Hippocampal Pyramidal Neurons

Voltage-Dependent Ca2+-Channel Block by Openers of Intermediate and Small Conductance Ca2+-Activated K+ Channels in Urinary Bladder Smooth Muscle Cells

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