apamin

..adaptation and slowed spontaneous firing, effects attributable to an increase in the amplitude and duration of an apamin-sensitive afterhyperpolarization...

..This provides a cellular framework to understand the functional consequences of altered SK3 expression, a candidate disease mechanism for schizophrenia...

..Immature type B cells had somewhat narrower spontaneous spikes that were followed by a delayed, apamin-sensitive AHP...

..Both effects of NO were mediated by inhibition of Ca-activated iberiotoxin- and apamin-sensitive K channels, but only inhibition of apamin-sensitive K channels fully mimicked all effects of NO on ..

..Pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (100 microM), apamin (0...

..In most tissues this neurotransmission is apamin-sensitive, but recent studies in human colonic circular smooth muscle (CSM) suggest the presence of apamin-..

..Our results reveal the functional role of SK channels with defined subunit compositions in some neurons and open the way to the identification of the molecular determinants of AHP currents in many brain regions...

..Whole-cell recording showed a sharp segregation of apamin-sensitive SK current within the hippocampal formation, in agreement with the SK2 distribution, suggesting that SK2 ..

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..This toxin distinguished between the SK channels underlying the apamin-sensitive I(AHP) and the Ca(2+)-activated K(+) channels mediating the slow I(AHP) (sI(AHP)) in hippocampal neurons...

..Thus, blocking SK channels facilitates the induction of long-term potentiation by enhancing NMDAR-dependent Ca(2+) signals within dendritic spines...

..of IK(Ca) and SK(Ca) channels using 10 microM TRAM-39 (2-(2-chlorophenyl)-2,2-diphenylacetonitrile) plus 100 nM apamin (leaving an iberiotoxin-sensitive component), whereas the response to substance P was abolished...

..The aim of this study was to determine if PAR-1 and PAR-2 mediate gastrointestinal smooth muscle relaxation and to clarify the underlying mechanisms...

Using field potential recording in the CA1-region of rat hippocampal slices we investigated the effect of apamin; a specific antagonist of small conductive calcium activated potassium channels on long-term potentiation (LTP)...

..IK channels were blocked by 2-5 mM external TEA and were sensitive to both charybdotoxin (100 nM) and apamin (500 nM)...

1. Our aim was to identify the small-conductance Ca(2+)-activated K(+) channel(s) (SK) underlying the apamin-sensitive afterhyperpolarization (AHP) in rat superior cervical ganglion (SCG) neurones. 2...

..The corresponding I(AHP) was sensitive to antagonism by CdCl2 (200 microM), apamin (0.3-1 microM), and dequalinium (3 microM)...

..Co-expression of rSK1 with rSK2 also changed the channel pharmacology. The sensitivity of SK current to block by apamin was reduced approximately 16-fold from an IC50 of 94 pM (for SK2 alone) to 1.4 nM (for SK2 and SK1 together)...

..kappa, was indistinguishable from the natural toxin when tested in vitro in competition assay with radiolabelled apamin for binding to rat brain synaptosomes (IC50 = 3 nM)...

..The most obvious distinguishing feature of this new isoform was that whereas hSK3 was blocked by apamin (Kd=0.8 nM), scyllatoxin (Kd=2.1 nM), and d-tubocurarine (Kd=33...

..Peptide toxins such as apamin and scyllatoxin, as well as organic compounds such as quaternary salts of bicuculline, dequalinium, UCL 1684 and ..

..We measured in vivo effects of apamin, a blocker of small-conductance (SK) K(Ca) channels, and charybdotoxin, a blocker of large-conductance K(Ca) ..

..The synaptic currents, as well as the inner hair cell's response to acetylcholine, are mediated by a nicotinic (alpha9-containing) receptor and result in the activation of small-conductance calcium-dependent potassium channels...

..3 Ca(2+) channels in its activation. On the basis of its high sensitivity to apamin (K(D) 360 pM) it was identified as a small-conductance Ca(2+)-activated K(+) current (SK), probably SK2...

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The purpose of the present study was to examine how apamin interacts with the three cloned subtypes of small-conductance Ca2+-activated K+ channels (hSK1, rSK2 and rSK3)...

..In heterologous expression systems, SK2 and SK3 currents are blocked by the bee venom toxin apamin, just as well as the corresponding neuronal AHP currents...

..The peptides apamin and charybdotoxin were used to distinguish the calcium-activated potassium channels involved in the acetylcholine ..

..This current was still present during superfusion of either IbTx (60 nm) or apamin (300 nm) but was abolished in Cs(+)-based intracellular solution or during superfusion of 5 mm TEA, suggesting the ..

..However, antagonists of small conductance Ca(2+)-activated K+ channels, apamin and d-tubocurarine, reduced the amplitude of the membrane afterhyperpolarization and inhibited the spike frequency ..

1. The apamin-sensitive small-conductance Ca(2+)-activated K(+) channel (SK(Ca)) was characterized in porcine coronary arteries. 2...

..The bee venom toxin apamin inhibits exclusively the three cloned SK channel subtypes (SK1, SK2, and SK3) with different affinity, highest for ..

..In order to assess whether apamin-sensitive K+ channels play a role in NO - induced relaxation of the human uterus, we have studied the effect of ..

..Maurotoxin did inhibit (86)Rb efflux (IC(50), 45 nM) through, and (125)I-apamin binding (K(i), 10 nM) to SK channels in low ionic strength buffers (i.e...

..The respiratory burst was markedly inhibited by blockers of SK2 (apamin) and SK4 channels (clotrimazole and charybdotoxin), and to a lesser extent, by the potent Kv1.3 blocker agitoxin-2.

The bee venom toxin apamin is an important drug tool for characterising small conductance Ca(2+)-activated K(+) channels (SK channels)...

..The relaxation was unaffected by specific inhibitors of IKCa (TRAM-34, 1 micromol/L) or SKCa (apamin, 50 nmol/L) alone or in combination...

..The channels that formed from the various subunits displayed differential sensitivity to apamin and tubocurare...

b>Apamin, a bee venom toxin which blocks a Ca2+-dependent K+ current, potentiates N-methyl-D-aspartate (NMDA)-induced burst firing in dopamine neurons...

..injection of 1,2-bis-(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA; fast Ca(2+) chelator), and by apamin (selective toxin for K(Ca) channels of the SK subtype)...

..from postnatal day 16 (P16)-P30 rats and held at 37 degrees C] and then treated with the SK KCa channel antagonist apamin or the SK KCa channel agonist 1-ethyl-2-benzimidazolinone or the Cav channel antagonists w-omega-conotoxin GVIA (..

b>Apamin blocks SK channels responsible for long-lasting hyperpolarization following the action potential. Using an olfactory associative task, the effect of an intracerebroventricular 0...

..Beside apamin, ScTX is a high affinity blocker of the SK2 channel, whereas CTX is unable to block current through SK2...

The solution structure of the bee venom neurotoxin apamin has been determined with a distance geometry program using distance constraints derived from NMR. Twenty embedded structures were generated and refined by using the program DSPACE...

..1-KCa2.3 (a.k.a. SK1-SK3) and the intermediate-conductance channel KCa3.1 (a.k.a. IKCa1). The apamin-sensitive KCa2 channels contribute to the medium afterhyperpolarization and are crucial regulators of neuronal ..

From a cDNA library prepared from venom glands of worker bees, clones encoding the precursors of apamin and MCD peptide have been isolated. The cDNAs are similar at the 5'-ends and identical in their 3'-regions...

..In contrast, only partial inhibition was observed with the BK and SK channel inhibitors, iberiotoxin and apamin, respectively...

..were tested for their ability to block actions mediated by the small conductance, apamin-sensitive Ca(2+)-activated K+ (SKCa) channels in rat cultured sympathetic neurones and guinea-pig isolated ..

..component of the sustained currents were Ca2+ dependent and sensitive to charybdotoxin and iberiotoxin but not to apamin, suggesting that they were mediated by large-conductance Ca2+-activated K+ (BK) channels...

..was mimicked by extraluminal application of tetraethylammonium or charybdotoxin but not by iberiotoxin, apamin, glibenclamide, barium, or 4-aminopirydine...

..Ca2+-dependent K+ channel blockers, charybdotoxin and apamin, a voltage-dependent K+ channel blocker, 4-aminopyridine, and a non-selective K+ channel blocker, ..

..To quantify structural and functional characteristics of the caudal artery from spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats with particular reference to endothelium-derived hyperpolarizing factor (EDHF)...

..The SK/IK channel-blockers apamin, dequalinium, and charybdotoxin caused increases in average [Ca(2+)](i) levels and in frequency of [Ca(2+)](i) ..

..In contrast, charybdotoxin and apamin (large and small conductance Ca(2+) activated-K(+) channel blockers, respectively), 4-aminopyridine or ..

..to anandamide was suppressed by combinations of vascular Ca(2+)-dependent K(+) channel blockers (including apamin+charybdotoxin+iberiotoxin or apamin+TRAM-34+iberiotoxin) (TRAM-34, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole)...

..In contrast, LNAME had no effect on the initial phase of ACH-induced dilation. In the presence of apamin + charybdotoxin, the initial vasodilator response to ACH (1 micromol/l) was diminished (ILA, from 108 +/- 8 to 46 +..

..The cloned and native channels are voltage-independent, Ca(2+)-activated, apamin-sensitive, show an equivalent voltage-dependent Ba(2+) block and possess a similar ion selectivity...

..It was hypothesized that ATP- and acetylcholine-activated Ca(2+)-signals are spatially separated and generated in plasma membrane regions with predominant localization of SK- and IR-channels, respectively...

..b>Apamin, an antagonist of type 2 small-conductance Ca2+-activated potassium (SK2) channels, also reduced hippocampal AHPs ..

..KEY RESULTS: A combination of apamin plus charybotoxin, which are, respectively, blockers of small-conductance and of intermediate- and large-..

..The K(+) current was blocked by a combination of charybdotoxin and apamin and appears to result from the opening of IK(Ca) and SK(Ca) channels...

..Therefore, somatostatin actions appear to be the entrainment of projection neurons to the rhythms generated by some interneurons. Somatostatin is then capable of modifying the processing and output of the neostriatum...

..of endothelium-dependent hyperpolarization-the Ca2+ -activated potassium channel (KCa) channel inhibitors, apamin and charybdotoxin...

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..Inhibition of EDHF with a combination of K(Ca) blockers, charybdotoxin (50 nM) plus apamin (50 nM), increased baseline vascular tone in MCT-induced hypertensive lungs...

..to inhibition by L-NNA or ODQ, but abolished by additional inhibition of K(Ca) channels with charybdotoxin plus apamin. 4...

..activation was also performed in presence of NG-nitro-L-Arginine, indomethacin, proadifen, hydroxocobalamin, apamin plus charybdotoxin, Hoe-140 or PD-123,319, as well as, after endocardial endothelium removal...

..The calcium-activated potassium (K(Ca)) antagonists charybdotoxin (ChTX) and apamin decreased the magnitude but not the duration of the hindlimb vasodilator response to ACh...

..However, blockers of IK(Ca) channels, charybdotoxin (ChTX), and of SK(Ca) channels, apamin (Ap), significantly reduced the whole-cell current...

..These results suggest that competition between cholinergic suppression of the sI(AHP) and cholinergic activation of the SK channels shapes the AHP and spike-frequency adaptation...

..Lowering extracellular [Ca(2+)] increased both I(NaP) and probability of bursting. We suggest that these mechanisms underlie burst generation in mastication and that similar processes may be found in other motor pattern generators...

..determined in anesthetized rats before and after acute intravenous infusion of either L-NAME or a combination of apamin plus charybdotoxin that would selectively inhibit EDHF...

..BmSKTx1 selectively inhibited apamin-sensitive SK currents in RACC with Kd of 0.72 microM and Hill coefficient of 2.2...

..The sHAP and spike-frequency adaptation were blocked by cadmium, as well as by the SK channel antagonist apamin. The fHAP was attenuated by the BK channel antagonist iberiotoxin (IbTX), by the BK/IK channel antagonist ..

..All four ciliary KCas were observed: The 16 pS channel, K0.5,Ca=40 microM and apamin-sensitive; the 30 and 50 pS channel, K0...

..We studied the intervention of nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factor (EDHF) in mediating responses to acetylcholine in thyroid arteries from euthyroid and methimazole-treated (MT) patients...

..to THC was inhibited by high K+ buffer, and by the following K+ channel inhibitors: charybdotoxin (100 nM), apamin (500 nM) and barium chloride (30 microM), but not by 4-aminopyridine, glibenclamide or tertiapin...

..reptiles and amphibians, acetylcholine released from efferent neurons inhibits hair cells via activation of an apamin-sensitive, calcium-dependent potassium current...

..However, local peripheral pretreatment of the paw with charybdotoxin and apamin (large- and small-conductance Ca2+-activated K+ channel inhibitors, respectively), 4-aminopyridine and ..

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..ACh (0.03-3 microM) induced a hyperpolarization through activations of both apamin- and charybdotoxin-sensitive Ca2+-activated K+ channels (K(Ca)) in rabbit AVECs...

..brain slices from PND 14-21 mice, long step depolarizations (100 ms) in the mitral cell soma evoked a cadmium- and apamin-sensitive outward SK current lasting several hundred milliseconds...

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..inhibited by the respective small-conductance and intermediate-conductance calcium- activated K+ channel blockers apamin and charybdotoxin...

..Tail currents presented a fast Ca(2+)-activated and apamin-sensitive component (I(AHP)) and were further reduced by carbachol...

..The dependency of this pathway on [Ca(2+)](o) is greater in the 66-h multinucleate syncytiotrophoblast-like cells, suggesting that the mechanism for Ca(2+) entry may be altered during differentiation of trophoblast cells...

..Charybdotoxin (10 nmol/l) and apamin (1...

..01 - 3 microM) was abolished by a combination of charybdotoxin (ChTX, 0.1 microM) plus apamin (Apa, 0.1 microM) and was inhibited by 68+/-6% (n=6) by 4-aminopyridine (4-AP, 5 mM). 3. ACh(0...

..Both were blocked by iberiotoxin, a specific blocker of large-conductance K(Ca) channels (BK), but not by apamin, a specific blocker of small-conductance K(Ca) channels. 4...

..In these cell types, hSK1 forms an apamin-sensitive channel with an IC(50) for apamin of 8 nM in HEK293 cells and 12 nM in COS-7 cells...

..b>Apamin (1 microM) reduced the E(max) without affecting the IC(50)...

..expressed 10 pS K+ channels that were Ca2+ dependent (EC(50) 630 nM) and were blocked by the SK channel inhibitor apamin (IC(50) 0.6 nM); whole cell SK3 currents inactivated at membrane potentials more positive than -40 mV...

..was blocked by external tetraethylammonium (TEA, 10 mM) and charybdotoxin (ChTX, 10 nM), but was not affected by apamin (50 nM)...

..current was abolished by the K(ATP) channel blocker tolbutamide, but not changed by the SK and BK channel blockers apamin or tetraethylammonium...

..effect on arteries contracted >10 mN, unless 100 nM iberiotoxin (IbTX), 100 nM charybdotoxin (ChTX), and/or 50 nM apamin were present...

..4 s. In 43% of those cells exhibiting an outward current, SK channel inhibitors, UCL 1848 (100 nM) and apamin (100 nM) abolished the outward current...

..A large part of this current was insensitive to iberiotoxin and apamin. The aim of the present study was to characterize the K(Ca) channel responsible for this current...

..To characterize the role of SK channels in UBSM, the effects of the SK channel blocker apamin on phasic contractions were examined...

..These results provide the first evidence of the developmental regulation and function of SK channels in central neurons...

..In Krebs solution, the Ca(2+)-activated K(+)-channel blocker, apamin (10 nM), abolished relaxant responses...

..3. In atropine-treated animals (6 micromol kg(-1), i.v., plus infusion of 1.8 micromol h(-1)), apamin (30 nmol kg(-1), i.v...

..Ethanol excitation is completely blocked by quinidine, but not by the other K channel blockers apamin, tetraethylammonium, barium or cesium...

..Ethanol excitation is completely blocked by quinidine, but not by the other K channel blockers apamin, tetraethylammonium, barium or cesium...

..demonstrated that acute morphine analgesia is antagonized by blockers of potassium channels such as glyburide and apamin. Consistent with this are in vitro observations that K+ channel antagonists prevent mu opioid-stimulated k+ efflux ..

..The cellular hallmark of these conditions is the appearance of receptors for the peptide toxin apamin, a potent blocker of small conductance calcium-activated potassium (SK) channels...

..relaxations and hyperpolarizations that are blocked by LO inhibitors, high extracellular K ([K]o) and apamin. Thus, the endothelium-dependent relaxations and hyperpolarizations to ACh and AA are mediated by a LO metabolite ..

..endothelium-dependent relaxations and hyperpolarizations that are blocked by LO and CYP inhibitors, high [K]o and apamin. Thus, these relaxations and hyperpolarizations are mediated by a LO metabolite of AA...

b>Apamin-sensitive small conductance Ca2+-activated K+ channels (SK channels) are implicated in the molecular and cellular mechanisms underlying learning and memory, and blocking SK channels in vivo affects hippocampal dependent learning ..

..The mechanisms of action may include phosphorylation and inactivation of the sK2 calcium-activated apamin-sensitive potassium channel...

..Blocking SK channels with apamin reduces the stimulus intensity that is required to induce NMDA receptor-dependent long-term potentiation at ..

..changes found in DM2 are part of a common pathway also affected in DM1; 5) to determine whether molecular changes affecting RNA splicing, CUG binding proteins, and apamin receptors are similar to those found in DM1.

..Subtypes of SK channels may be distinguished by different sensitivities to the bee venom peptide toxin apamin. Application of apamin to regions of the brain alters physiologically important processes, such as sleep patterns ..

..In the second specific aim, current and voltage clamp techniques will be used to test the hypothesis that an apamin-insensitive Ca2+-dependent conductance: (1) contributes to the hyperpolarization that terminates the plateau phase ..

..Our preliminary findings indicate that the SK channel blocker, apamin enhances memory, while the SK channel activator, 1-EBIO impairs memory...

..Our preliminary findings indicate that the SK channel blocker, apamin enhances memory, while the SK channel activator, 1-EBIO impairs memory...

..In CA1 hippocampal pyramidal neurons (HPNs) the AHP has two kinetic components. The medium AHP is apamin-sensitive and is not affected by neurotransmitter-induced second messengers, while the slow AHP is insensitive to ..

..SK can be reduced by drugs like apamin or by depletion of intracellular calcium...