Cholesterol is a structural component of cellular membranes particularly enriched in synapses but its role in synaptic transmission remains poorly understood. We used rat hippocampal cultures and their acute cholesterol depletion by methyl-β-cyclodextrin as a tool to describe the physiological role of cholesterol in glutamatergic synaptic transmission. Cholesterol proved to be a key molecule for the function of synapses as its depletion resulted in a significant reduction of both NMDA receptor (NMDAR) and AMPA/kainate receptor-mediated evoked excitatory postsynaptic currents (eEPSCs), by 94% and 72%, respectively. We identified two presynaptic and two postsynaptic steps of synaptic transmission which are modulated by cholesterol and explain together the above-mentioned reduction of eEPSCs. In the postsynapse, we show that physiological levels of cholesterol are important for maintaining the normal probability of opening of NMDARs and for keeping NMDARs localized in synapses. In the presynapse, our results favour the hypothesis of a role of cholesterol in the propagation of axonal action potentials. Finally, cholesterol is a negative modulator of spontaneous presynaptic glutamate release. Our study identifies cholesterol as an important endogenous regulator of synaptic transmission and provides insight into molecular mechanisms underlying the neurological manifestation of diseases associated with impaired cholesterol synthesis or decomposition.

• MeSH
• AMPA receptory metabolismus   MeSH
• cholesterol farmakologie   MeSH
• excitační postsynaptické potenciály účinky léků   MeSH
• hipokampus účinky léků   metabolismus   MeSH
• krysa rodu Rattus MeSH
• kyselina glutamová metabolismus   MeSH
• mozková kůra účinky léků   metabolismus   MeSH
• nervový přenos * MeSH
• neurony účinky léků   metabolismus   MeSH
• potkani Wistar MeSH
• presynaptická zakončení účinky léků   metabolismus   MeSH
• receptory N-methyl-D-aspartátu metabolismus   MeSH
• synapse účinky léků   metabolismus   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
• AMPA receptory MeSH
• cholesterol MeSH
• kyselina glutamová MeSH
• receptory N-methyl-D-aspartátu MeSH

Acute morphine exposure induces antinociceptive activity, but the underlying mechanisms in the central nervous system are unclear. Using whole-cell patch clamp recordings, we explore the role of morphine in the modulation of excitatory synaptic transmission in lateral amygdala neurons of rats. The results demonstrate that perfusion of 10 microM of morphine to the lateral amygdala inhibits the discharge frequency significantly. We further find that there are no significant influences of morphine on the amplitude of spontaneous excitatory postsynaptic currents (sEPSCs). Interestingly, morphine shows no marked influence on the evoked excitatory postsynaptic currents (eEPSCs) in the lateral amygdala neurons. These results indicate that acute morphine treatment plays an important role in the modulation on the excitatory synaptic transmission in lateral amygdala neurons of rats.

• MeSH
• amygdala účinky léků   fyziologie   MeSH
• excitační postsynaptické potenciály účinky léků   fyziologie   MeSH
• krysa rodu Rattus MeSH
• morfin farmakologie   MeSH
• opioidní analgetika farmakologie   MeSH
• orgánové kultury - kultivační techniky MeSH
• potkani Sprague-Dawley MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• morfin MeSH
• opioidní analgetika MeSH

The relationship between the activity of the lumbar spinal interneurones and propriospinal (PS) and spino-bulbo-spinal (SBS) efferent reflex responses evoked by somatic (muscle, skin) and splanchnic nerve stimulation was studied in chloralose-anaestetized adult cats. During stimulation of one somatic nerve, the postsynaptic cord elements could be divided into three groups, according to whether their activity was was synchronous with the PS component of the efferent discharge (PS group), with the SBS component (SBS group) or with both (PS-SBS-group). Group SBS and PS-SBS interneurones were localized in the ventral quadrant of the grey matter. On stimulation of different nerves, the same interneurone could in one case respond synchronously with the PS component of the efferent discharge and in another with the SBS component. The membrane of units which did not generate propagated spike potentials during PS or SBS reflex activity was hyperpolarized in this period, or failed to display changes characteristic for postsynaptic inhibition. Convergence of somatic and visceral afferentation was observed in all three groups of postsynaptic elements. In type PS-SBS and SBS units it was massive (occurring in 85% and 100% of the cases respectively). The results confirmed the intimacy of functional contact of PS and SBS systems activated by somatic and visceral afferents.

• MeSH
• evokované potenciály MeSH
• fyzikální stimulace MeSH
• interneurony fyziologie   MeSH
• kočky MeSH
• kůže inervace   MeSH
• medulla oblongata fyziologie   MeSH
• membránové potenciály MeSH
• mícha fyziologie   MeSH
• motorické neurony fyziologie   MeSH
• nervový přenos MeSH
• neurony eferentní fyziologie   MeSH
• reflex * MeSH
• splanchnické nervy fyziologie   MeSH
• svaly inervace   MeSH
• synapse fyziologie   MeSH
• zvířata MeSH
• Check Tag
• kočky MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

The interaction of visceral and somatic afferentation at the level of postsynaptic spinal cord elements was studied in cats. The effect of conditioning stimuli on the propriospinal (PS) and suprasegmental (SS) component of the tested unit responses was compared. Afferentation from the splanchnic nerve completely inhibited the SS component of somatomotor motoneuronal responses; the PS component was only partly inhibited. Inhibition persisted even after the conditioning stimulus-induced changes in the membrane potential of the motoneurones had disappeared. The activity of the interneurones responsing synchronously with the SS component of the efferent discharges was also completely inhibited in the same intervals. The inhibitory effect of splanchnic afferentation on the PS component of interneuronal discharges evoked by the stimulation of somatic afferents was significantly less effective. The results of interaction for test responses from the cutaneous and muscular nerves was the same. When splanchnic responses were tested during conditioning from somatosensory areas, inhibitory control was found to be reciprocal. The authors discuss the question of the structures and mechanisms participating in functional relations between the autonomic and somatic nervous system in the spinal cord.

• MeSH
• aferentní nervové dráhy fyziologie   MeSH
• elektrická stimulace MeSH
• interneurony fyziologie   MeSH
• kočky MeSH
• kůže inervace   MeSH
• membránové potenciály MeSH
• mícha fyziologie   MeSH
• motorické neurony fyziologie   MeSH
• splanchnické nervy fyziologie   MeSH
• svaly inervace   MeSH
• zvířata MeSH
• Check Tag
• kočky MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články 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

Glutamate AMPA receptors are critical for sensory transmission at the spinal cord dorsal horn (DH). Plasma membrane AMPA receptor endocytosis that can be induced by insulin may underlie long term modulation of synaptic transmission. Insulin receptors (IRs) are known to be expressed on spinal cord DH neurons, but their possible role in sensory transmission has not been studied. In this work the effect of insulin application on fast excitatory postsynaptic currents (EPSCs) mediated by AMPA receptors evoked in DH neurons was evaluated. Acute spinal cord slices from 6 to 10 day old mice were used to record EPSCs evoked in visually identified superficial DH neurons by dorsal root primary afferent stimulation. AMPA EPSCs could be evoked in all of the tested neurons. In 75% of the neurons the size of the AMPA EPSCs was reduced to 62.1% and to 68.9% of the control values when 0.5 or 10 microM insulin was applied. There was no significant change in the size of the AMPA EPSCs in the remaining 25% of DH neurons. The membrane permeable protein tyrosine kinase inhibitor, lavendustin A (10 microM), prevented the insulin induced AMPA EPSC depression. Our results suggest a possible role of the insulin pathway in modulation of sensory and nociceptive synaptic transmission in the spinal cord.

• MeSH
• AMPA receptory účinky léků   metabolismus   MeSH
• bolest metabolismus   patofyziologie   MeSH
• buňky zadních rohů míšních účinky léků   metabolismus   MeSH
• excitační postsynaptické potenciály účinky léků   fyziologie   MeSH
• fenoly farmakologie   MeSH
• inhibitory enzymů farmakologie   MeSH
• inzulin metabolismus   farmakologie   MeSH
• kyselina glutamová metabolismus   MeSH
• metoda terčíkového zámku MeSH
• myši MeSH
• nervové receptory účinky léků   metabolismus   MeSH
• nervový přenos účinky léků   fyziologie   MeSH
• novorozená zvířata MeSH
• orgánové kultury - kultivační techniky MeSH
• receptor inzulinu účinky léků   metabolismus   MeSH
• signální transdukce účinky léků   fyziologie   MeSH
• tyrosinkinasy antagonisté a inhibitory   metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AMPA receptory MeSH
• fenoly MeSH
• inhibitory enzymů MeSH
• inzulin MeSH
• kyselina glutamová MeSH
• lavendustin A MeSH Prohlížeč
• receptor inzulinu MeSH
• tyrosinkinasy MeSH

N-methyl-d-aspartate (NMDA) receptors (NMDARs) are highly expressed in the CNS and mediate the slow component of excitatory transmission. The present study was aimed at characterizing the temperature dependence of the kinetic properties of native NMDARs, with special emphasis on the deactivation of synaptic NMDARs. We used patch-clamp recordings to study synaptic NMDARs at layer II/III pyramidal neurons of the rat cortex, recombinant GluN1/GluN2B receptors expressed in human embryonic kidney (HEK293) cells, and NMDARs in cultured hippocampal neurons. We found that time constants characterizing the deactivation of NMDAR-mediated excitatory postsynaptic currents (EPSCs) were similar to those of the deactivation of responses to a brief application of glutamate recorded under conditions of low NMDAR desensitization (whole-cell recording from cultured hippocampal neurons). In contrast, the deactivation of NMDAR-mediated responses exhibiting a high degree of desensitization (outside-out recording) was substantially faster than that of synaptic NMDA receptors. The time constants characterizing the deactivation of synaptic NMDARs and native NMDARs activated by exogenous glutamate application were only weakly temperature sensitive (Q(10)=1.7-2.2), in contrast to those of recombinant GluN1/GluN2B receptors, which are highly temperature sensitive (Q(10)=2.7-3.7). Ifenprodil reduced the amplitude of NMDAR-mediated EPSCs by approximately 50% but had no effect on the time course of deactivation. Analysis of GluN1/GluN2B responses indicated that the double exponential time course of deactivation reflects mainly agonist dissociation and receptor desensitization. We conclude that the temperature dependences of native and recombinant NMDAR are different; in addition, we contribute to a better understanding of the molecular mechanism that controls the time course of NMDAR-mediated EPSCs.

• MeSH
• antagonisté excitačních aminokyselin farmakologie   MeSH
• buněčné linie MeSH
• excitační postsynaptické potenciály účinky léků   fyziologie   MeSH
• hipokampus účinky léků   fyziologie   MeSH
• kinetika MeSH
• krysa rodu Rattus MeSH
• kultivované buňky MeSH
• kyselina glutamová metabolismus   MeSH
• lidé MeSH
• mozková kůra účinky léků   fyziologie   MeSH
• nervový přenos účinky léků   fyziologie   MeSH
• piperidiny farmakologie   MeSH
• potkani Wistar MeSH
• pyramidové buňky účinky léků   fyziologie   MeSH
• receptory N-methyl-D-aspartátu metabolismus   MeSH
• synapse účinky léků   fyziologie   MeSH
• techniky in vitro MeSH
• teplota * MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antagonisté excitačních aminokyselin MeSH
• ifenprodil MeSH Prohlížeč
• kyselina glutamová MeSH
• piperidiny MeSH
• receptory N-methyl-D-aspartátu MeSH

Long-term potentiation (LTP) in the rat hippocampus is the most extensively studied cellular model for learning and memory. Induction of classical LTP involves an NMDA-receptor- and calcium-dependent increase in functional synaptic AMPA receptors, mediated by enhanced recycling of internalized AMPA receptors back to the postsynaptic membrane. Here we report a physiologically relevant NMDA-receptor-independent mechanism that drives increased AMPA receptor recycling and LTP. This pathway requires the metabotropic action of kainate receptors and activation of G protein, protein kinase C and phospholipase C. Like classical LTP, kainate-receptor-dependent LTP recruits recycling endosomes to spines, enhances synaptic recycling of AMPA receptors to increase their surface expression and elicits structural changes in spines, including increased growth and maturation. These data reveal a new and, to our knowledge, previously unsuspected role for postsynaptic kainate receptors in the induction of functional and structural plasticity in the hippocampus.

• MeSH
• AMPA receptory metabolismus   MeSH
• dendritické trny metabolismus   MeSH
• dlouhodobá potenciace fyziologie   MeSH
• endozomy metabolismus   MeSH
• fosfolipasy typu C metabolismus   MeSH
• hipokampus fyziologie   MeSH
• krysa rodu Rattus MeSH
• kultivované buňky MeSH
• neurony metabolismus   fyziologie   MeSH
• proteinkinasa C metabolismus   MeSH
• proteiny vázající GTP metabolismus   MeSH
• receptory kyseliny kainové fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• AMPA receptory MeSH
• fosfolipasy typu C MeSH
• proteinkinasa C MeSH
• proteiny vázající GTP MeSH
• receptory kyseliny kainové MeSH

It has been shown previously that 3,4-diaminopyridine (3,4-DAP) facilitates synaptic transmission in the frog sympathetic ganglion inducing so-called stimulus-bound repetition (SBR), i.e. a brief burst of repetitive postganglionic discharges after a single orthodromic stimulus. In the present study we analyzed one of the possible mechanisms of the 3,4-DAP-induced SBR, namely changes in postsynaptic membrane excitability. We found that 3,4-DAP in concentration optimal for inducing SBR (2 X 10(-4) mol.l-1) had no direct effect on the excitability of the postsynaptic membrane of frog sympathetic neurones. The excitability was expressed as the threshold for action potentials elicited orthodromically, antidromically and directly, as well as the spike activity evoked by constant depolarizing current pulses. We also indirectly excluded the involvement of two other possible mechanisms of neuronal membrane excitability modulation in the 3,4-DAP-induced SBR, i.e. the M-current suppression by analyzing the participation of muscarinic receptor activation in the SBR, and inhibition of the Ca(2+)-activated K+ currents by measuring the duration of afterhyperpolarization of antidromic action potential. Our findings indicate that no remarkable changes in the properties of the postsynaptic membrane contribute to the generation of 3,4-DAP-induced SBR in the frog sympathetic ganglion. This strongly supports the hypothesis that the mechanism underlying SBR evoked by this drug is presynaptic.

• MeSH
• 4-aminopyridin analogy a deriváty   farmakologie   MeSH
• akční potenciály MeSH
• amifampridin MeSH
• draslíkové kanály účinky léků   MeSH
• nervový přenos MeSH
• Rana esculenta MeSH
• Rana temporaria MeSH
• sympatická ganglia fyziologie   MeSH
• synaptické membrány fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 4-aminopyridin MeSH
• amifampridin MeSH
• draslíkové kanály MeSH

Leaky integrate-and-fire neuronal models with reversal potentials have a number of different diffusion approximations, each depending on the form of the amplitudes of the postsynaptic potentials. Probability distributions of the first-passage times of the membrane potential in the original model and its diffusion approximations are numerically compared in order to find which of the approximations is the most suitable one. The properties of the random amplitudes of postsynaptic potentials are discussed. It is shown on a simple example that the quality of the approximation depends directly on them.

• MeSH
• akční potenciály fyziologie   MeSH
• difuze MeSH
• lidé MeSH
• matematika MeSH
• membránové potenciály fyziologie   MeSH
• modely neurologické * MeSH
• neurony fyziologie   MeSH
• normální rozdělení MeSH
• počítačová simulace MeSH
• Poissonovo rozdělení MeSH
• pravděpodobnost MeSH
• stochastické procesy MeSH
• synaptické potenciály MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH