共查询到10条相似文献,搜索用时 93 毫秒
1.
It is well documented that prolonged alteration of activity in neuronal networks initiates a number of homeostatic mechanisms including compensatory changes of excitatory and inhibitory synaptic strength. We studied whether this also evokes compensatory changes of short-term synaptic transmission. Using patch-clamp technique in hippocampal cell cultures we examined the effects: of prolonged decrease of neuronal firing evoked by sodium channel blocker: tetrodotoxin (TTX) and ionotropic glutamate receptor antagonist - kynurenate; prolonged enhancement ofneuronal firing evoked by antagonist GABAA receptors - bicuculline on short-term depression of GABAergic synaptic transmission evoked by train of stimuli (5 Hz). We found that both TTX and kynurenate treatments enhance depression of GABAergic transmission, while bicuculline treatment does not. We conclude that alteration of depression of GABAergic transmission evoked by the prolonged decrease of neuronal activity may contribute to homeostatic plasticity in hippocampal neuronal networks. 相似文献
2.
Paired pulse depression (PPD) of GABA-ergic IPSC was studied in rat hippocampal cell cultures. Synaptic responses were evoked by local extracellular stimulation of the presynaptic units; a whole-cell patch-clamp technique was employed to record responses (IPSC) from the postsynaptic neurons. Paired stimulation (100-msec-long interstimulus interval) resulted in depression of the second IPSC amplitude (IPSC2). This was usually accompanied by an increase in the coefficient of variation (CV) of IPSC2 comparing with that of IPSC1. These results support the involvement of presynaptic mechanism(s) in PPD and suggest a possibility to use PPD alteration as an indicator for the presynaptic origin of modulatory effects. To check this suggestion, we tested whether alteration of the quantum content would affect PPD. We found that reduction of the transmitter release by application of Cd2+ decreased PPD. Post-tetanic potentiation, a well-established presynaptic phenomenon, increased PPD. We conclude that PPD changes may be used as a test for the involvement of presynaptic changes. 相似文献
3.
Storozhuk MV Ivanova SY Piomelli D 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2005,55(5):581-585
Brief depolarization of postsynaptic neurons in hippocampus and cerebellum results in a transient depression of GABAergic inhibitory input, called "depolarization-induced suppression of inhibition" (DSI). We studied whether a similar phenomenon occurs in the rat neocortical neurons. Using patch-clamp technique in neocortical cell cultures we examined the effects of a 5-second depolarization of postsynaptic neurons on evoked GABAergic inhibitory post-synaptic currents (IPSCs). We found that the depolarization evoked a suppression of IPSC amplitude in 6 out of 26 neuronal pairs tested. The suppression of IPSC amplitude lasted for approximately 70 seconds and was accompanied by changes of paired-pulse ratio and IPSC coefficient of variation (CV), which is suggestive of a presynaptic mechanism. These results are in agreement with previous observations in hippocampal cell cultures and suggest that neocortical neurons express DSI. 相似文献
4.
Vanilloid receptors 1 (VRs1) expressed in a subpopulation of sensory neurons and responsible for processing of chemical and
thermal noxious stimuli were also shown to be expressed in several cerebral structures and to be involved in the regulation
of glutamatergic synaptic transmission. In this study, we started to investigate the possibility that VRs1 are also involved
in the regulation of GABA-ergic synaptic transmission. For this purpose, the effect of a VR1 agonist, capsaicin, on spontaneous
GABA-ergic inhibitory postsynaptic currents (IPSCs) was studied in hippocampal cell cultures using a patch-clamp technique.
It was found that capsaicin (10 μM) decreased both the frequency and amplitude of spontaneous IPSCs. This finding suggests
the involvement of VRs1 in the regulation of neuronal firing in some GABA-ergic interneurons and in the modulation of the
efficacy of GABA-ergic synaptic transmission. However, considering the direction of the effect (a decrease in the IPSC frequency)
and lack of its desensitization, the involvement of other receptor(s) also cannot currently be ruled out.
Neirofiziologiya/Neurophysiology, Vol. 38, No. 4, pp. 364–367, July–August, 2006. 相似文献
5.
Local presynaptic activity gates homeostatic changes in presynaptic function driven by dendritic BDNF synthesis 总被引:1,自引:0,他引:1
Jakawich SK Nasser HB Strong MJ McCartney AJ Perez AS Rakesh N Carruthers CJ Sutton MA 《Neuron》2010,68(6):1143-1158
Homeostatic synaptic plasticity is important for maintaining stability of neuronal function, but heterogeneous expression mechanisms suggest that distinct facets of neuronal activity may shape the manner in which compensatory synaptic changes are implemented. Here, we demonstrate that local presynaptic activity gates a retrograde form of homeostatic plasticity induced by blockade of AMPA receptors (AMPARs) in cultured hippocampal neurons. We show that AMPAR blockade produces rapid (<3 hr) protein synthesis-dependent increases in both presynaptic and postsynaptic function and that the induction of presynaptic, but not postsynaptic, changes requires coincident local activity in presynaptic terminals. This "state-dependent" modulation of presynaptic function requires postsynaptic release of brain-derived neurotrophic factor (BDNF) as a retrograde messenger, which is locally synthesized in dendrites in response to AMPAR blockade. Taken together, our results reveal a local crosstalk between active presynaptic terminals and postsynaptic signaling that dictates the manner by which homeostatic plasticity is implemented at synapses. 相似文献
6.
I. V. Mel'nik 《Neurophysiology》1991,23(3):205-213
The spontaneous development of synaptic activity (SSA) was studied in cell cultures of chick embryo spinal cord. The complicated time structure of the SSA, an important early-stage characteristic of which was giant inhibitory postsynaptic currents (IPSC), was demonstrated. The ionic nature and pharmacological sensitivity of these IPSC suggest that glycine is their transmitter. Emergence of excitatory postsynaptic currents (EPSC) and complex antagonistic relationships between excitatory and inhibitory SSA was detected later. Possible mechanisms for maintenance of synaptic activity during the inhibitory function are discussed. Correlations between the regularities of synaptic transmission development that we have disclosed and neuronal circuit electrical activity are examined.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 3, pp. 280–290, May–June, 1991. 相似文献
7.
Several forms of short-term synaptic plasticity of GABA-ergic synaptic transmission selectively expressed only in a fraction
of synaptic connections have been described earlier. In particular, this is the phenomenon termed “depolarization-induced
suppression of inhibition” (DSI), a transient suppression of GABA-ergic synaptic transmission evoked by postsynaptic spike
firing or brief depolarization of the membrane of postsynaptic neurons. On the other hand, the same tetanic stimulation (30 sec−1, 4 sec) of the presynaptic neuron also revealed the heterogeneity of GABA-ergic synaptic connections: about 45% of the connections
were facilitated, while 55% were depressed. In this work, we show that post-tetanic depression is predominantly expressed
in neuronal pairs susceptible to DSI, and that both phenomena have a similar time course. Considering our own results and
the retrograde involvement of endocannabinoids in DSI, we hypothesize that post-tetanic depression is also due to the release
of endocannabinoids acting, in the latter case, on their autoreceptors. 相似文献
8.
At present, there are no direct methods to determine the number of synaptic receptor-related channels activated in the course
of synaptic transmission (N) or a value of the single-channel conductance (γ). Peak-scaled nonstationary fluctuation analysis (PS NSFA) should be considered
the most well-developed indirect approach used for estimating these parameters. Despite the relatively wide using of this
approach for the analysis of various synaptic currents, some aspects of possible errors that can occur in the course of data
acquisition or their subsequent processing have not been studied. We examined in detail the problem of applicability of PS
NSFA in the study of spontaneous and evoked GABA-ergic inhibitory postsynaptic currents (IPSCs). IPSCs were recorded using
a dual patch-clamp technique from hippocampal neurons growing in low-density cultures. Parameters of the recorded IPSCs and
values for different components of GABA-ergic synaptic transmission reported earlier were used for simulations and PS-NSFA
analysis. In Monte Carlo computer simulations of evoked IPSCs, the influence of series resistance, background noise, asynchronicity
of transmitter release, GABAA channel properties, dendritic attenuation, and instrumental filtering on γ estimates obtained by PS NSFA was examined. We
concluded that the γ and, consequently, N values may be satisfactorily estimated by the suggested approach using spontaneous and evoked IPSCs recorded in inhibitory
synaptic connections in hippocampal cultures within a wide range of experimental conditions. We also estimated the mean of
the single-channel conductance of synaptic GABAA receptors in neurons from primary hippocampal cultures and found that this value (29 ± 5 pS) agrees well with the high conductance
of single synaptic GABAA receptors observed in acute hippocampal slices. This indicates that dissociated cultures are an adequate model for studying
the properties of synaptic GABAA receptors.
Neirofiziologiya/Neurophysiology, Vol. 37, No. 4, pp. 379–388, July–August, 2004. 相似文献
9.
Synaptic activity in the central nervous system undergoes rapid state-dependent changes, requiring constant adaptation of the homeostasis between excitation and inhibition. The underlying mechanisms are, however, largely unclear. Chronic changes in network activity result in enhanced production of the inhibitory transmitter GABA, indicating that presynaptic GABA content is a variable parameter for homeostatic plasticity. Here we tested whether such changes in inhibitory transmitter content do also occur at the fast time scale required to ensure inhibition-excitation-homeostasis in dynamic cortical networks. We found that intense stimulation of afferent fibers in the CA1 region of mouse hippocampal slices yielded a rapid and lasting increase in quantal size of miniature inhibitory postsynaptic currents. This potentiation was mediated by the uptake of GABA and glutamate into presynaptic endings of inhibitory interneurons (the latter serving as precursor for the synthesis of GABA). Thus, enhanced release of inhibitory and excitatory transmitters from active networks leads to enhanced presynaptic GABA content. Thereby, inhibitory efficacy follows local neuronal activity, constituting a negative feedback loop and providing a mechanism for rapid homeostatic scaling in cortical circuits. 相似文献
10.
Presynaptic inhibition of neurotransmitter release is thought to be mediated by a reduction of axon terminal Ca2+ current. We have compared the actions of several known inhibitors of evoked glutamate release with the actions of the Ca2+ channel antagonist Cd2+ on action potential-independent synaptic currents recorded from CA3 neurons in hippocampal slice cultures. Baclofen and adenosine decreased the frequency of miniature excitatory postsynaptic currents (mEPSCs) without affecting the distribution of their amplitudes. Cd2+ blocked evoked synaptic transmission, but had no effect on the frequency or amplitude of either mEPSCs or inhibitory postsynaptic currents (IPSCs). Inhibition of presynaptic Ca2+ current therefore appears not to be required for the inhibition of glutamate release by adenosine and baclofen. Baclofen had no effect on the frequency of miniature IPSCs, indicating that gamma-aminobutyric acid B-type receptors exert distinct presynaptic actions at excitatory and inhibitory synapses. 相似文献