The role of negatively charged amino acids in the F-loop of the beta 4 subunit in channel activation and desensitization was studied using the patch-clamp technique. The selected amino acids were changed to their neutral analogs via point mutations. Whole-cell currents were recorded in COS cells transiently transfected with the alpha 3 beta 4 nicotinic acetylcholine receptor. The application of acetylcholine (ACh), nicotine (Nic), cytisine (Cyt), carbamylcholine (CCh) and epibatidine (Epi) to cells clamped at -40 mV produced inward currents which displayed biphasic desensitization. The EC50 of Epi and Nic were increased by a factor of 3-6 due to mutations D191N or D192N. Only Epi remained an agonist in the double-mutated receptors with EC50 increased 17-fold. The interaction of the receptors with the competitive antagonist (+)tubocurarine (TC) was weakened almost 3-fold in the double-mutated receptors. The mutations increased the proportion of the slower desensitization component and increased the response plateau, resulting in decreased receptor desensitization. The double mutation substantially accelerated the return from long-term desensitization induced by Epi.

• MeSH
• aminokyseliny chemie   metabolismus   MeSH
• bicyklické sloučeniny heterocyklické farmakologie   MeSH
• Cercopithecus aethiops MeSH
• COS buňky MeSH
• kinetika MeSH
• krysa rodu Rattus MeSH
• molekulární sekvence - údaje MeSH
• mutace genetika   MeSH
• neurony metabolismus   MeSH
• nikotin farmakologie   MeSH
• nikotinové receptory chemie   metabolismus   MeSH
• nikotinoví agonisté farmakologie   MeSH
• podjednotky proteinů chemie   metabolismus   MeSH
• pyridiny farmakologie   MeSH
• sekundární struktura proteinů MeSH
• sekvence aminokyselin MeSH
• sekvenční seřazení MeSH
• tubokurarin farmakologie   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aminokyseliny MeSH
• bicyklické sloučeniny heterocyklické MeSH
• epibatidine MeSH Prohlížeč
• nikotin MeSH
• nikotinové receptory MeSH
• nikotinoví agonisté MeSH
• podjednotky proteinů MeSH
• pyridiny MeSH
• tubokurarin MeSH

After anticholinesterase treatment, depolarization of the postsynaptic muscle membrane by about 5 mV develops due to non-quantally released acetylcholine from the motor nerve terminal and can be revealed as hyperpolarization by the addition of curare (H-effect). The H-effect increases significantly to 8.7 mV after inhibition of NO-synthase by L-nitroarginine methylester (L-NAME) whilst no changes in the amplitude and frequency of quantal miniature endplate potentials are observed.

• MeSH
• acetylcholin metabolismus   MeSH
• bránice inervace   MeSH
• cholinesterasové inhibitory farmakologie   MeSH
• inhibitory enzymů farmakologie   MeSH
• krysa rodu Rattus MeSH
• membránové potenciály účinky léků   MeSH
• nedepolarizující myorelaxancia farmakologie   MeSH
• nervosvalové spojení účinky léků   metabolismus   MeSH
• nervová zakončení metabolismus   MeSH
• NG-nitroargininmethylester farmakologie   MeSH
• potkani Wistar MeSH
• receptory neurotransmiterů antagonisté a inhibitory   fyziologie   MeSH
• synthasa oxidu dusnatého antagonisté a inhibitory   MeSH
• tubokurarin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acetylcholin MeSH
• cholinesterasové inhibitory MeSH
• inhibitory enzymů MeSH
• nedepolarizující myorelaxancia MeSH
• NG-nitroargininmethylester MeSH
• receptory neurotransmiterů MeSH
• synthasa oxidu dusnatého MeSH
• tubokurarin MeSH

In mammalian nerve-muscle preparations treated with an anticholinesterase, the acetylcholine (ACh) released non-quantally (NQR) reaches the postsynaptic receptors and causes a small depolarization of the membrane potential at the endplate region of the muscle fibres. Increase in quantal release potentiates the NQR and vice versa, the amplitude and the kinetic parameters of quantal miniature endplate currents (MEPCs) change during manipulation of NQR, indicating direct interaction between both types of release. Repetitive binding of ACh to postsynaptic receptors which prolongs the time course of MEPCs in anti-cholinesterase-treated endplates leads within 1-2 h to progressive desensitization in the presence of non-quantal release and to the subsequent shortening of the quantal responses. We have also investigated the effect of procedures known to modulate non-quantal acetylcholine release, on the small, but obvious, difference in the resting membrane potential between the endplate zone and other areas of the mouse muscle fibre. The resting membrane potential at the endplate zone with intact cholinesterase is more negative (by 2-4 mV) than in the endplate-free area. The experiments were performed to test the hypothesis that the hyperpolarization is caused by an electrogenic Na(+)-K+ pump operating during the action of ACh released in non-quantal form. Observations in favour of this idea are that both short-term denervation (which eliminates non-quantal but not quantal release) and ouabain abolish the local synaptic hyperpolarization and that subsequent application of low doses of ACh restores it. It follows, therefore, that the hyperpolarization is probably caused by a small but continuous ACh leakage from the nerve terminal.

• MeSH
• acetylcholin metabolismus   farmakologie   MeSH
• bránice fyziologie   MeSH
• denervace svalu MeSH
• elektrofyziologie MeSH
• hořčík farmakologie   MeSH
• membránové potenciály účinky léků   MeSH
• myši MeSH
• nedepolarizující myorelaxancia farmakologie   MeSH
• nervosvalová ploténka fyziologie   MeSH
• ouabain farmakologie   MeSH
• sodíko-draslíková ATPasa antagonisté a inhibitory   fyziologie   MeSH
• stereoizomerie MeSH
• synaptické membrány fyziologie   MeSH
• tubokurarin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acetylcholin MeSH
• hořčík MeSH
• nedepolarizující myorelaxancia MeSH
• ouabain MeSH
• sodíko-draslíková ATPasa MeSH
• tubokurarin MeSH

• MeSH
• acetylcholin metabolismus   MeSH
• cholinesterasové inhibitory farmakologie   MeSH
• krysa rodu Rattus MeSH
• membránové potenciály MeSH
• motorické neurony účinky léků   metabolismus   MeSH
• nervová zakončení metabolismus   MeSH
• nikotinové receptory účinky léků   fyziologie   MeSH
• piperidiny farmakologie   MeSH
• rychlost sekrece účinky léků   MeSH
• tetrodotoxin farmakologie   MeSH
• tubokurarin farmakologie   MeSH
• vápník fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetylcholin MeSH
• cholinesterasové inhibitory MeSH
• nikotinové receptory MeSH
• piperidiny MeSH
• tetrodotoxin MeSH
• tubokurarin MeSH
• vápník MeSH
• vesamicol MeSH Prohlížeč

1. Rat hemidiaphragms were incubated in a physiological low-K+ medium without stimulation and the amount of acetylcholine (ACh) released was measured radioenzymatically. Cholinesterases were inhibited by paraoxon. 2. In the presence of 1 microM tetrodotoxin (TTX), the amount of ACh released during a 2 h incubation was lowered by 40%. A similar decrease was observed in the absence of Ca2+ and in the presence of 10 microM-d-tubocurarine (dTC). The effects of TTX combined with Ca2+ removal, and of TTX combined with dTC were no greater than those of TTX, dTC or Ca2+ removal alone. TTX and dTC had no effect on the release of ACh from diaphragms 4 days after denervation. 3. The reduction of spontaneous ACh release observed in the presence of TTX or dTC or in the absence of Ca2+ is best interpreted on the assumption that about 40% of the ACh release was due to the impulse activity known to be generated in intramuscular motor nerve branches by the ACh which accumulates after the inhibition of cholinesterases. 4. In the presence of 1 and 10 microM vesamicol (AH5183, 2-(4-phenylpiperidino)-cyclohexanol), the release of ACh was also diminished by approximately 40%. Vesamicol did not augment the inhibition of release produced by TTX or by the omission of Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

• MeSH
• acetylcholin metabolismus   MeSH
• bránice MeSH
• časové faktory MeSH
• chemická deprese MeSH
• cholinesterasy fyziologie   MeSH
• denervace MeSH
• depolarizující myorelaxancia farmakologie   MeSH
• krysa rodu Rattus MeSH
• piperidiny farmakologie   MeSH
• potkani Wistar MeSH
• svaly inervace   metabolismus   MeSH
• techniky in vitro MeSH
• tetrodotoxin farmakologie   MeSH
• tubokurarin farmakologie   MeSH
• vápník fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acetylcholin MeSH
• cholinesterasy MeSH
• depolarizující myorelaxancia MeSH
• piperidiny MeSH
• tetrodotoxin MeSH
• tubokurarin MeSH
• vápník MeSH
• vesamicol MeSH Prohlížeč

The continuous administration of d-tubocurarine (6.5 +/- 0.4 mg/kg e.w./24 h) to chick embryos from the 4th to the 12th day of incubation had a positive effect on defects produced in the development of spontaneous motility either by decentralization of the spinal cord or by chemical phenobarbital depression, or by a combination of both experimental factors. In normal embryos, d-tubocurarine had no effect on the development of spontaneous motility.

• MeSH
• fenobarbital MeSH
• kuřecí embryo fyziologie   MeSH
• orgánové kultury - kultivační techniky MeSH
• pohyb účinky léků   MeSH
• tubokurarin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• kuřecí embryo fyziologie   MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fenobarbital MeSH
• tubokurarin MeSH

Apamin, a specific blocker of one class of Ca(2+)-activated K+ channes, was used to detect the apamin receptors associated with K+ channels in the mucosa of the rat jejunum and colon. Two receptor sites for 125I-apamin have been identified. These sites differed in their affinity for apamin (jejunum: KD1 = 1.1 nM and KD2 = 170 nM; colon: KD1 = 0.5 nM and KD2 = 1.1 nM and KD2 = 140 nM) and the maximum number of sites (jejunum: B(max1) = 111 and B(max2) = 4030; colon: B(max1) = 187 and B(max2) = 7550 fmol/mg of protein). 125I-apamin binding was stimulated by K+ ions with K0.5 = 1.0 mM and inhibited by the neuromuscular blocker tubocurarine (KI = 50 microM). We interpret these data to demonstrate that the high-affinity, low-capacity binding sites reflect the existence of apamin-sensitive K+ channels in the intestinal mucosa.

• MeSH
• apamin metabolismus   MeSH
• draslík farmakologie   MeSH
• draslíkové kanály metabolismus   MeSH
• inbrední kmeny potkanů MeSH
• jejunum MeSH
• kinetika MeSH
• kolon MeSH
• krysa rodu Rattus MeSH
• receptory neurotransmiterů účinky léků   metabolismus   MeSH
• střevní sliznice chemie   účinky léků   metabolismus   MeSH
• tubokurarin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• apamin receptor MeSH Prohlížeč
• apamin MeSH
• draslík MeSH
• draslíkové kanály MeSH
• receptory neurotransmiterů MeSH
• tubokurarin MeSH

• MeSH
• corpus striatum účinky léků   MeSH
• inbrední kmeny potkanů MeSH
• krysa rodu Rattus MeSH
• tubokurarin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• tubokurarin MeSH

• MeSH
• arousal účinky léků   fyziologie   MeSH
• azoly aplikace a dávkování   MeSH
• barbituráty aplikace a dávkování   MeSH
• benzodiazepiny aplikace a dávkování   MeSH
• elektroencefalografie MeSH
• isatin aplikace a dávkování   MeSH
• krysa rodu Rattus MeSH
• tubokurarin aplikace a dávkování   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• azoly MeSH
• barbituráty MeSH
• benzodiazepiny MeSH
• isatin MeSH
• tubokurarin MeSH

The subsynaptic area of mouse diaphragm fibres was hyperpolarized by 1--2 mV during local curarization of the junctional zone in the presence of the reversible anticholinesteraze prostigmine (6 X 10(-6) M), or after treatment of the muscle with organophosphate cholinesterase inhibitor Soman. In a solution containing 5 mM K+ the mean hyperpolarization was 1.1 +/- 0.27 mV at mean resting potential--70 mV. After adding 2 X 10(-5) M ouabain the hyperpolarization increased to 1.5 +/- 0.25 mV. Removal of potassium ions from the bathing medium also increased curare induced hyperpolarization to 1.80 +/- 0.40 mV. Reactivation of membrane ATP-ase by addition of K+ after a period in K+-free medium reduced the hyperpolarization to zero, where measurements were performed 10--20 min after the readdition. It was concluded that spontaneous non-quantal leakage of acetylcholine occurs at the mouse neuromuscular junction, as it does in the frog (ref. Katz and Miledi 1977). Conditions which block the Na+-K+-dependent ATP-ase of nerve terminals increased the continuous leakage of ACh and activation of the pump decreased it.

• MeSH
• adenosintrifosfatasy metabolismus   MeSH
• bránice enzymologie   metabolismus   fyziologie   MeSH
• cholinesterasové inhibitory farmakologie   MeSH
• draslík farmakologie   MeSH
• elektrofyziologie MeSH
• membránové potenciály účinky léků   MeSH
• myši MeSH
• neostigmin farmakologie   MeSH
• neurotransmiterové látky metabolismus   MeSH
• ouabain farmakologie   MeSH
• sodíko-draslíková ATPasa antagonisté a inhibitory   MeSH
• techniky in vitro MeSH
• tubokurarin farmakologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• adenosintrifosfatasy MeSH
• cholinesterasové inhibitory MeSH
• draslík MeSH
• neostigmin MeSH
• neurotransmiterové látky MeSH
• ouabain MeSH
• sodíko-draslíková ATPasa MeSH
• tubokurarin MeSH