共查询到20条相似文献,搜索用时 15 毫秒
1.
Acetylcholine (ACh) contributes to learning processes by modulating cortical plasticity in terms of intensity of neuronal activity and selectivity properties of cortical neurons. However, it is not known if ACh induces long term effects within the primary visual cortex (V1) that could sustain visual learning mechanisms. In the present study we analyzed visual evoked potentials (VEPs) in V1 of rats during a 4–8 h period after coupling visual stimulation to an intracortical injection of ACh analog carbachol or stimulation of basal forebrain. To clarify the action of ACh on VEP activity in V1, we individually pre-injected muscarinic (scopolamine), nicotinic (mecamylamine), α7 (methyllycaconitine), and NMDA (CPP) receptor antagonists before carbachol infusion. Stimulation of the cholinergic system paired with visual stimulation significantly increased VEP amplitude (56%) during a 6 h period. Pre-treatment with scopolamine, mecamylamine and CPP completely abolished this long-term enhancement, while α7 inhibition induced an instant increase of VEP amplitude. This suggests a role of ACh in facilitating visual stimuli responsiveness through mechanisms comparable to LTP which involve nicotinic and muscarinic receptors with an interaction of NMDA transmission in the visual cortex. 相似文献
2.
The present study describes the effects of gamma-aminobutyric acid (GABA) and its antagonists, bicuculline and 2-hydroxysaclofen,
on visual responses of neurons in the pigeon nucleus lentiformis mesencephali (nLM). The results indicate that GABA significantly
reduces both spontaneous activity and visual responsiveness, and GABAA antagonist bicuculline but not GABAB antagonist 2-hydroxysaclofen enhances visual responses of nLM cells examined. Furthermore, inhibition produced by motion
in the null-direction of pretectal neurons is diminished by bicuculline but not by 2-hydroxysaclofen. It is therefore concluded
that the null-direction inhibition of directional cells in the pigeon nLM is predominantly mediated by GABA and GABAA receptors. This inhibition may at least in part underlie directional asymmetry of optokinetic responses. 相似文献
3.
Kharauzov AK Shelepin IuE Pronin SV Krasil'nikov NN Murav'eva SV 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2001,87(2):261-270
Dichoptic stimulation was used in comparison of visual evoked potentials (VEPs) with those obtained with monocular stimulation (recordings made from the occipital area). 16 subjects viewed sinusoidal gratings with the right eye while a visual noise was added via a mirror for the left eye. In presence of the noise, amplitude of the early VEP components' N1, P1b, and the late component P2 decreased, P1a is not changed in presence of the noise, and the late negative wave N2 increased for all spatial frequencies. The effect of noise on the amplitude of VEPs obtained for monocular and dichoptic stimulation was similar. The data suggest that external noise is filtered by the V1 cortical neurons--matched filters for the gratings. 相似文献
4.
Propofol is a widely used intravenous general anesthetic. Propofol-induced unconsciousness in humans is associated with inhibition of thalamic activity evoked by somatosensory stimuli. However, the cellular mechanisms underlying the effects of propofol in thalamic circuits are largely unknown. We investigated the influence of propofol on synaptic responsiveness of thalamocortical relay neurons in the ventrobasal complex (VB) to excitatory input in mouse brain slices, using both current- and voltage-clamp recording techniques. Excitatory responses including EPSP temporal summation and action potential firing were evoked in VB neurons by electrical stimulation of corticothalamic fibers or pharmacological activation of glutamate receptors. Propofol (0.6 – 3 μM) suppressed temporal summation and spike firing in a concentration-dependent manner. The thalamocortical suppression was accompanied by a marked decrease in both EPSP amplitude and input resistance, indicating that a shunting mechanism was involved. The propofol-mediated thalamocortical suppression could be blocked by a GABAA receptor antagonist or chloride channel blocker, suggesting that postsynaptic GABAA receptors in VB neurons were involved in the shunting inhibition. GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) were evoked in VB neurons by electrical stimulation of the reticular thalamic nucleus. Propofol markedly increased amplitude, decay time, and charge transfer of GABAA IPSCs. The results demonstrated that shunting inhibition of thalamic somatosensory relay neurons by propofol at clinically relevant concentrations is primarily mediated through the potentiation of the GABAA receptor chloride channel-mediated conductance, and such inhibition may contribute to the impaired thalamic responses to sensory stimuli seen during propofol-induced anesthesia. 相似文献
5.
A. E. Medvedev V. I. Shvedov T. M. Chulkova O. A. Fedotova E. Saederup R. F. Squires 《Neurochemical research》1996,21(12):1521-1526
The effects of pirlindole and dehydro-pirlindole on GABAA receptors and MAO-A activity were investigated in vitro. Pirlindole was inactive as a GABA antagonist. Dehydro-pirlindole
exhibited partial and selective blockade of a subset of GABAA receptors with an EC50 of 12μM and maximum reversal (ΔBopt) of 42%. Inhibition of rat brain and human placenta MAO-A by both compounds was much more potent (with IC50 range 0.3–0.005 μM). Their effects on MAO-A activity were partially reversible in vitro. In contrast to pirlindole, dehydro-pirlindole
may act not only as MAO-A inhibitor but also as a clozapine-like selective GABAA receptor blocker, preferentially blocking a subset of GABAA receptors that are not sensitive to DMCM or Ro 5-4864.
Pirlindole is the generic name of the drug pyrazidol. 相似文献
6.
《Electronic Notes in Theoretical Computer Science》1995,96(1):1-5
Multichannel recordings of visual evoked potentials (VEPs) have proved to be useful in the evaluation of visual field defects. We studied the topographic distribution of transient VEPs in 15 migraine patients (8 with visual aura and 7 without) and 15 age-matched controls during the migraine-free interval. All the subjects included in the study had normal visual fields. VEPs were recorded from 9 electrodes placed on the posterior scalp. Stimuli were full-field and hemifield reversing square wave grating patterns of medium spatial frequency (4 c/deg). The groups did not show significant differences in latencies and amplitudes of the major components (N70, P100) recorded from the midline. However, migraine patients with visual hemianopic aura showed definite asymmetries in the VEP amplitude distribution. Significantly reduced, absent or polarity-invered VEP responses were recorded ipsilateral to the side of the prodromic visual symptoms. Direct comparison of affected and unaffected hemispheres by partial field stimulation confirmed these findings. According to the VEP cortical generator theory, these abnormalities suggest a functional anomaly consistent with the clinical syndrome and detectable also in the migraine-free interval. None of the migraine patients without aura or the controls showed VEP amplitude asymmetries. We conclude that multichannel VEP recordings may discriminate between different subtypes of migraine and contribute important physiopathological information to the study of this disease. 相似文献
7.
Y Yanovsky SR Schubring Q Yao Y Zhao S Li A May HL Haas JS Lin OA Sergeeva 《PloS one》2012,7(8):e42512
Since ancient times ursodeoxycholic acid (UDCA), a constituent of bile, is used against gallstone formation and cholestasis. A neuroprotective action of UDCA was demonstrated recently in models of Alzheimer''s disease and retinal degeneration. The mechanisms of UDCA action in the nervous system are poorly understood. We show now that UDCA promotes wakefulness during the active period of the day, lacking this activity in histamine-deficient mice. In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABAAR antagonist gabazine. In histaminergic neurons recorded in slices UDCA reduced amplitude and duration of spontaneous and evoked IPSCs. In acutely isolated histaminergic neurons UDCA inhibited GABA-evoked currents and sIPSCs starting at 10 µM (IC50 = 70 µM) and did not affect NMDA- and AMPA-receptor mediated currents at 100 µM. Recombinant GABAA receptors composed of α1, β1–3 and γ2L subunits expressed in HEK293 cells displayed a sensitivity to UDCA similar to that of native GABAA receptors. The mutation α1V256S, known to reduce the inhibitory action of pregnenolone sulphate, reduced the potency of UDCA. The mutation α1Q241L, which abolishes GABAAR potentiation by several neurosteroids, had no effect on GABAAR inhibition by UDCA. In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABAA receptors. 相似文献
8.
《Electronic Notes in Theoretical Computer Science》1991,80(2):81-88
Pattern electroretinograms (P-ERGs) and visual evoked potentials (VEPs) to 4 Hz alternating square-wave gratings were simultaneously recorded in 23 subjects. Responses were Fourier analyzed and amplitude and phase of the 2nd and 4th temporal harmonics were measured.The spatial frequency-amplitude function of the P-ERG 2nd harmonic component displayed either a bandpass tuning behavior, or a low-pass behavior. The peak amplitude for subjects with bandpass tuning was at 1.5 c/deg. The phase of the P-ERG 2nd harmonic decreased monotonically as spatial frequency increased. The VEP 2nd harmonic had a bimodal spatial frequency function with a peak at 3 c/deg and a second increase at spatial frequencies below 1 c/deg, regardless of the P-ERG characteristics. The phase of VEP 2nd and 4th harmonic had an inverted U-shaped function with peak at 3 c/deg and 1.5 c/deg respectively.Comparison of simultaneously recorded P-ERG and VEP spatial frequency functions demonstrated different tuning behavior for cortical and retinal responses. It is concluded that the proposed technique permits the separate analysis of retinal and cortical processing of visual information. The 2nd and 4th harmonic components of VEP behave independently of each other suggesting they may be generated by different subsystems. 相似文献
9.
《Electronic Notes in Theoretical Computer Science》1997,104(4):375-380
We investigated the effect of cholinergic agents on the cat visual evoked potentials (VEPs) recorded from the primary visual cortex (V1) and lateral geniculate nucleus dorsalis (LGNd) to determine on which level of the visual pathway the cholinergic system acts. VEPs to the alternation of 0.1 cycles per degree sinusoidal gratings at 1 and 4 Hz were recorded from N2O-anesthetized cats directly from the surface of V1 and LGNd. The depth of recording in LGNd was determined by the site where the maximal response was obtained by 1 Hz stimulation. VEPs to 4 Hz stimulation, which showed sinusoidal waveforms and were analyzed by fast Fourier transforms, were used as indicators for modulation by cholinergic agents. Physostigmine, an acetylcholinesterase inhibitor, 0.7 mg/kg i.v., suppressed the amplitude of the responses more at V1 (suppression ratio: mean±SD, 85.4±9.3%) than at LGNd (32.4±30.7%) (P<0.05). Conversely, scopolamine, a muscarinic receptor blocker, 0.7 mg/kg i.v., increased the amplitude of the responses more at V1 (enhancement ratio: mean±SD, 60.3±22.3%) than at LGNd (−22.2±22.5%) (P<0.05). These results indicate that the V1 changes reflect a direct cortical cholinergic effect, probably by modulating the cholinergic projection from the nucleus basalis of Meynert to V1. 相似文献
10.
Interaction with the gamma-aminobutyric-acid-type-A (GABAA) receptors is recognized as an important component of the mechanism of propofol, a sedative-hypnotic drug commonly used as anesthetic. However the contribution of GABAA receptors to the central nervous system suppression is still not well understood, especially in the thalamocortical network. In the present study, we investigated if intracerebral injection of bicuculline (a GABAA receptor antagonist) into the thalamus ventral posteromedial nucleus (VPM, a thalamus specific relay nuclei that innervated S1 mostly) could reverse propofol-induced cortical suppression, through recording the changes of both spontaneous and somatosensory neural activities in rat’s somatosensory cortex (S1). We found that after injection of bicuculline into VPM, significant increase of neural activities were observed in all bands of local field potentials (total band, 182±6%), while the amplitude of all components in somatosensory evoked potentials were also increased (negative, 121±9% and positive, 124±6%).These data support that the potentiation of GABAA receptor-mediated synaptic inhibition in a thalamic specific relay system seems to play a crucial role in propofol-induced cortical suppression in the somatosensory cortex of rats. 相似文献
11.
Gain modulation by nicotine in macaque v1 总被引:4,自引:0,他引:4
Acetylcholine is a ubiquitous cortical neuromodulator implicated in cognition. In order to understand the potential for acetylcholine to play a role in visual attention, we studied nicotinic acetylcholine receptor (nAChR) localization and function in area V1 of the macaque. We found nAChRs presynaptically at thalamic synapses onto excitatory, but not inhibitory, neurons in the primary thalamorecipient layer 4c. Furthermore, consistent with the release enhancement suggested by this localization, we discovered that nicotine increases responsiveness and lowers contrast threshold in layer 4c neurons. We also found that nAChRs are expressed by GABAergic interneurons in V1 but rarely by pyramidal neurons, and that nicotine suppresses visual responses outside layer 4c. All sensory systems incorporate gain control mechanisms, or processes which dynamically alter input/output relationships. We demonstrate that at the site of thalamic input to visual cortex, the effect of this nAChR-mediated gain is an enhancement of the detection of visual stimuli. 相似文献
12.
《Electronic Notes in Theoretical Computer Science》1991,80(3):167-180
Visual evoked potentials (VEPs) to pattern reversal vertical bar stimuli of 3 different sizes (1, 2, 4 c/deg) were recorded from 19 scalp derivations in 50 controls. The stimuli were presented on a full-field (FF) screen of 24° visual angle, and on left and right half-fields (HF) of 12° radius. In 15 controls partial HF stimuli were presented on the central 3 and 6° and as hemiannular stimuli of 12° with occlusion of the central 3 and 6°.An antero-posterior polarity reversal of the N1-P1-N2 sequence was observed for FF VEPs. A tangential polarity reversal was observed for HF VEPs. Also with central or hemiannular stimuli polarity reversals of all VEP components were observed within the scalp.Variants of VEP distribution, absence of prominence of some of the ipsi- or contralateral VEP components were observed in 8–40% of controls.The FF and HF VEP distribution, and the variant VEP asymmetries were partly dependent on the pattern spatial frequency. 相似文献
13.
Sriharsha Kantamneni Immaculada M. Gonzàlez-Gonzàlez Jia Luo Helena Cimarosti Susan C. Jacobs Nadia Jaafari Jeremy M. Henley 《The Journal of biological chemistry》2014,289(10):6681-6694
Inhibitory GABAB receptors (GABABRs) can down-regulate most excitatory synapses in the CNS by reducing postsynaptic excitability. Functional GABABRs are heterodimers of GABAB1 and GABAB2 subunits and here we show that the trafficking and surface expression of GABABRs is differentially regulated by synaptic or pathophysiological activation of NMDA receptors (NMDARs). Activation of synaptic NMDARs using a chemLTP protocol increases GABABR recycling and surface expression. In contrast, excitotoxic global activation of synaptic and extrasynaptic NMDARs by bath application of NMDA causes the loss of surface GABABRs. Intriguingly, exposing neurons to extreme metabolic stress using oxygen/glucose deprivation (OGD) increases GABAB1 but decreases GABAB2 surface expression. The increase in surface GABAB1 involves enhanced recycling and is blocked by the NMDAR antagonist AP5. The decrease in surface GABAB2 is also blocked by AP5 and by inhibiting degradation pathways. These results indicate that NMDAR activity is critical in GABABR trafficking and function and that the individual subunits can be separately controlled to regulate neuronal responsiveness and survival. 相似文献
14.
Sixteen known 5-HT3 receptor blockers, including clozapine, fully or partially reverse the inhibitory effect of 1 M GABA on [35S]TBPS binding, indicating that they are also GABAA antagonists, some of them selective for subsets of GABAA receptors. The 5-HT3 receptor blocker, ondansetron, has been reported to produce some antipsychotic and anxiolytic effects. However, no antipsychotic effects have been reported for a large number of highly potent 5-HT3 receptor blockers. Like clozapine, ondansetron partially reverses the inhibitory effect of GABA on [35S]TBPS binding. Additivity experiments suggest that ten 5-HT3 receptor blockers tested at low concentrations preferentially block subtypes of GABAA receptors that are among those blocked by clozapine. Wiley and Porter (29) reported that MDL-72222, the most potent GABAA antagonist decribed here, partially generalizes (71%) with clozapine in rats trained to discriminate an interoceptive clozapine stimulus, but only at a dose that severly decreases responding. Tropisetron (ICS-205,930) exhibits both GABA-positive and GABA-negative effects. R-(+)-zacopride is 6-fold more potent than S-(–)-zacopride as a GABAA antagonist. We conclude that the observed antipsychotic and, possibly, anxiolytic effects of some 5-HT3 receptor blockers are due to selective antagonism of certain GABAA receptors, and not to blockade of 5-HT3 receptors. We speculate that the anxiolytic and sedative effects of clozapine and several other antipsychotic drugs may be due to selective blockade of 122 GABAA receptors which are preferentially located on certain types of GABAergic interneurons (probably parvalbumin positive). Blockade of these receptors will increase the inhibitory output of these interneurons. So far, no highly potent GABAA antagonists with clozapine-like selectivity have been identified. Such compounds may exhibit improved clozapine-like antipsychotic activity. 相似文献
15.
Cho S Kim S Jin Z Yang H Han D Baek NI Jo J Cho CW Park JH Shimizu M Jin YH 《Biochemical and biophysical research communications》2011,(4):637-642
Isoliquiritigenin (ILTG) is a chalcone compound and has valuable pharmacological properties such as antioxidant, anti-inflammatory, anticancer, and antiallergic activities. Recently, the anxiolytic effect of ILTG has been reported; however, its action mechanism and hypnotic activity have not yet been demonstrated. Therefore, we investigated the hypnotic effect and action mechanism of ILTG. ILTG significantly potentiated the pentobarbital-induced sleep in mice at doses of 25 and 50 mg/kg. The hypnotic activity of ILTG was fully inhibited by flumazenil (FLU), a specific gamma-aminobutyric acid type A (GABAA)–benzodiazepine (BZD) receptor antagonist. The binding affinity of ILTG was 0.453 μM and was found to be higher than that of the reference compound, diazepam (DZP, 0.012 μM). ILTG (10−5 M) potentiated GABA-evoked currents to 151% of the control level on isolated dorsal raphe neurons. ILTG has 65 times higher affinity for GABAA–BZD receptors than DZP, and the dissociation constant for ILTG was 4.0 × 10−10 M. The effect of ILTG on GABA currents was blocked by 10−7 M FLU and ZK-93426. These results suggest that ILTG produces hypnotic effects by positive allosteric modulation of GABAA–BZD receptors. 相似文献
16.
17.
Scalp-recorded oscillatory potentials evoked by transient pattern-reversal visual stimulation in man
《Electronic Notes in Theoretical Computer Science》1995,96(3):206-218
Replicable oscillatory potentials, time-locked to pattern stimuli (9.0° central; counterphase reversal at 2.13 Hz) were dissociated from conventional, broad-band VEPs recorded in healthy volunteers at occipital scalp locations by high-pass digital filtering at 17.0–20.0 Hz. Nine consecutive wavelets were identified with a 56.4 ± 8.4 msec mean latency of the first replicable wavelet and mean peak-to-peak amplitude varying between 0.9 and 2.0 μV. The first 2 wavelets had significantly shorter latencies than wave N70 of unfiltered VEP, whereas the last 2 wavelets had longer latencies than N145. Latency and amplitude values varied as a function of contrast and spatial frequency of the stimulus, with shorter latencies and larger amplitudes at 60–90% contrast level and tuning of amplitude at 5.0 c/deg. All wavelets were correlated with wave P100 of unfiltered VEP, while a correlation with N70 of VEP was observed only for those wavelets with latencies in the range of wave P100. Two patients with documented brain lesions involving the visual system are described as examples of oscillatory responses occurring irrespective of filter bandpass and instead of the expected conventional VEP when the generation of these is interfered with by brain pathology. A substantial cortical contribution to the origin of the oscillatory response is conceivable. It is suggested that the oscillatory response to pattern-reversal stimulation reflects events in the visual system that are parallel to, and partly independent of, the conventional VEP, with potential application in research or for clinical purposes. 相似文献
18.
The brain GABAA receptor (GABAAR) is a key element of signaling and neural transmission in health and disease. Recently, complete sequence analysis of the recombinant GABAAR has been reported, separation and mass spectrometrical (MS) characterisation from tissue, however, has not been published so far. Hippocampi were homogenised, put on a sucrose gradient 10–69% and the layer from 10 to 20% was used for extraction of membrane proteins by a solution of Triton X‐100, 1.5 M aminocaproic acid in the presence of 0.3 M Bis‐Tris. This mixture was subsequently loaded onto blue native PAGE (BN‐PAGE) with subsequent analysis on denaturing gel systems. Spots from the 3‐DE electrophoretic run were stained with Colloidal Coomassie Brilliant Blue, and spots with an apparent molecular weight between 40 and 60 kDa were picked and in‐gel digested with trypsin, chymotrypsin and subtilisin. The resulting peptides were analysed by nano‐LC‐ESI‐MS/MS (ion trap) and protein identification was carried out using MASCOT searches. In addition, known GABAAR‐specific MS information taken from own previous studies was used for searches of GABAAR subunits. β‐1, β‐2 and β‐3, θ and ρ‐1 subunits were detected and six novel phosphorylation sites were observed and verified by phosphatase treatment. The method used herein enables identification of several GABAAR subunits from mouse hippocampus along with phosphorylations of β‐1 (T227, Y230), β‐2 (Y215, T439) and β‐3 (T282, S406) subunits. The procedure forms the basis for GABAAR studies at the protein chemical rather than at the immunochemical level in health and disease. 相似文献
19.
Hui Zhao Kousaku Ohinata Masaaki Yoshikawa 《Prostaglandins & other lipid mediators》2009,88(3-4):68-72
We found that prostaglandin (PG) D2, the most abundant PG produced in the central nervous system (CNS), exhibited anxiolytic-like activity at a dose of 10–100 pmol/mouse after intracerebroventricular (i.c.v.) administration in the elevated plus-maze test in mice. A DP1 receptor-selective agonist, BW245C, mimicked the anxiolytic-like activity of PGD2, while a DP2 receptor agonist 13,14-dihydro-15-keto-PGD2 was inactive. The anxiolytic-like activity of PGD2 was blocked by a DP1 antagonist, BWA868C, suggesting that PGD2-induced anxiolytic-like activity was mediated by the DP1 receptor. Adenosine A2A or GABAA receptor antagonists, SCH58261 or bicuculline, respectively, also blocked its anxiolytic-like activity. Taken together, centrally administered PGD2 may induce anxiolytic-like activity via the A2A and GABAA receptors, downstream of the DP1 receptor. 相似文献
20.
Caffeine analogs: effects on ryanodine-sensitive calcium-release channels and GABAA receptors 总被引:2,自引:0,他引:2
1. Caffeine at 0.3–10 mM enhanced the binding of [3H]ryanodine to calcium-release channels of rabbit muscle sarcoplasmic reticulum. A variety of other xanthines were as efficacious as caffeine or nearly so, but none appeared markedly more potent.2. Caffeine at 1 mM markedly inhibited binding of [3H]diazepam to GABAA receptors in rat cerebral cortical membranes.3. Other xanthines also inhibited binding with certain dimethylpropargylxanthines being nearly fivefold more potent than caffeine.4. Caffeine at 1 mM stimulated binding of [35S]TBPS to GABAA receptors as did certain other xanthines.5. The dimethylpropargylxanthines had little effect. 1,3-Dipropy1-8-cyclopentylxan- thine at 100 M had no effect on [3H]diazepam binding, but markedly inhibited [35S]TBPS binding.6. Structure–activity relationships for xanthines do differ for calcium-release channels and and for different sites on GABAA receptors, but no highly selective lead compounds were identified. 相似文献