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An Optogenetic Approach for Investigation of Excitatory and Inhibitory Network GABA Actions in Mice Expressing Channelrhodopsin-2 in GABAergic Neurons. J Neurosci 2017; 36:5961-73. [PMID: 27251618 DOI: 10.1523/jneurosci.3482-15.2016] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 04/12/2016] [Indexed: 01/16/2023] Open
Abstract
UNLABELLED To investigate excitatory and inhibitory GABA actions in cortical neuronal networks, we present a novel optogenetic approach using a mouse knock-in line with conditional expression of channelrhodopsin-2 (ChR2) in GABAergic interneurons. During whole-cell recordings from hippocampal and neocortical slices from postnatal day (P) 2-P15 mice, photostimulation caused depolarization and excitation of interneurons and evoked barrages of postsynaptic GABAergic currents. Excitatory/inhibitory GABA actions on pyramidal cells were assessed by monitoring the alteration in the frequency of EPSCs during photostimulation of interneurons. We found that in slices from P2-P8 mice, photostimulation evoked an increase in EPSC frequency, whereas in P9-P15 mice the response switched to a reduction in EPSC frequency, indicating a developmental excitatory-to-inhibitory switch in GABA actions on glutamatergic neurons. Using a similar approach in urethane-anesthetized animals in vivo, we found that photostimulation of interneurons reduces EPSC frequency at ages P3-P9. Thus, expression of ChR2 in GABAergic interneurons of mice enables selective photostimulation of interneurons during the early postnatal period, and these mice display a developmental excitatory-to-inhibitory switch in GABA action in cortical slices in vitro, but so far show mainly inhibitory GABA actions on spontaneous EPSCs in the immature hippocampus and neocortex in vivo SIGNIFICANCE STATEMENT We report a novel optogenetic approach for investigating excitatory and inhibitory GABA actions in mice with conditional expression of channelrhodopsin-2 in GABAergic interneurons. This approach shows a developmental excitatory-to-inhibitory switch in the actions of GABA on glutamatergic neurons in neocortical and hippocampal slices from neonatal mouse pups in vitro, but also reveals inhibitory GABA actions in the neonatal mouse neocortex and hippocampus in vivo.
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In vitro seizure like events and changes in ionic concentration. J Neurosci Methods 2015; 260:33-44. [PMID: 26300181 DOI: 10.1016/j.jneumeth.2015.08.014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/06/2015] [Accepted: 08/12/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND In vivo, seizure like events are associated with increases in extracellular K(+) concentration, decreases in extracellular Ca(2+) concentration, diphasic changes in extracellular sodium, chloride, and proton concentration, as well as changes of extracellular space size. These changes point to mechanisms underlying the induction, spread and termination of seizure like events. METHODS We investigated the potential role of alterations of the ionic environment on the induction of seizure like events-considering a review of the literature and own experimental work in animal and human slices. RESULTS Increasing extracellular K(+) concentration, lowering extracellular Mg(2+) concentration, or lowering extracellular Ca(2+) concentration can induce seizure like events. In human tissue from epileptic patients, elevation of K(+) concentration induces seizure like events in the dentate gyrus and subiculum. A combination of elevated K(+) concentration and 4-AP or bicuculline can induce seizure like events in neocortical tissue. CONCLUSIONS These protocols provide insight into the mechanisms involved in seizure initiation, spread and termination. Moreover, pharmacological studies as well as studies on mechanisms underlying pharmacoresistance are feasible.
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Moretto MB, Rossato JI, Nogueira CW, Zeni G, Rocha JBT. Voltage-dependent ebselen and diorganochalcogenides inhibition of 45Ca2+ influx into brain synaptosomes. J Biochem Mol Toxicol 2004; 17:154-60. [PMID: 12815611 DOI: 10.1002/jbt.10073] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
By mediating the Ca(2+) influx, Ca(2+) channels play a central role in neurotransmission. Chemical agents that potentially interfere with Ca(2+) homeostasis are potential toxic agents. In the present investigation, changes in Ca(2+) influx into synaptosomes by organic forms of selenium and tellurium were examined under nondepolarizing and depolarizing conditions induced by high KCl concentration (135 mM) or by 4-aminopyridine (4-AP). Under nondepolarizing conditions, ebselen (400 micro M) increased Ca(2+) influx; diphenyl ditelluride (40-400 micro M) decreased Ca(2+) in all concentrations tested; and diphenyl diselenide decreased Ca(2+) influx at 40 and 100 micro M, but had no effect at 400 micro M. In the presence of KCl as depolarizing agent, ebselen and diphenyl ditelluride decreased Ca(2+) influx in a linear fashion. In contrast, diphenyl diselenide did not modify Ca(2+) influx into isolated nerve terminals. In the presence of 4-AP (3 mM) as depolarizing agent, ebselen (400 micro M) caused a significant increase, whereas diphenyl diselenide and diphenyl ditelluride inhibited Ca(2+) influx into synaptosomes. The results can be explained by the fact that the mechanism through which 4-AP and high K(+) induced elevation of intracellular Ca(2+) is not exactly coincident. The mechanism by which diphenyl ditelluride and ebselen interact with Ca(2+) channel is unknown, but may be related to reactivity with critical sulfhydryl groups in the protein complex. The results of the present study indicate that the effects of organochalcogenides were rather complex depending on the condition and the depolarizing agent used.
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Affiliation(s)
- M B Moretto
- Departamento de Química, Centro de Ciencias Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
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Müller M, Dierkes PW, Schlue WR. Ionic mechanism of 4-aminopyridine action on leech neuropile glial cells. Brain Res 1999; 826:63-73. [PMID: 10216197 DOI: 10.1016/s0006-8993(99)01234-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Extracellular 4-aminopyridine (4-AP), tetraethylammonium chloride (TEA) and quinine depolarized the neuropile glial cell membrane and decreased its input resistance. As 4-AP induced the most pronounced effects, we focused on the action of 4-AP and clarified the ionic mechanisms involved. 4-AP did not only block glial K+ channels, but also induced Na+ and Ca2+ influx via other than voltage-gated channels. The reversal potential of the 4-AP-induced current was -5 mV. Application of 5 mM Ni2+ or 0.1 mM d-tubocurarine reduced the 4-AP-induced depolarization and the associated decrease in input resistance. We therefore suggest that 4-AP mediates neuronal acetylcholine release, apparently by a presynaptic mechanism. Activation of glial nicotinic acetylcholine receptors contributes to the depolarization, the decrease in input resistance, and the 4-AP-induced inward current. Furthermore, the 4-AP-induced depolarization activates additional voltage-sensitive K+ and Cl- channels and 4-AP-induced Ca2+ influx could activate Ca2+-sensitive K+ and Cl- channels. Together these effects compensate and even exceed the 4-AP-mediated reduction in K+ conductance. Therefore, the 4-AP-induced depolarization was paralleled by a decreasing input resistance.
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Affiliation(s)
- M Müller
- Institut für Neurobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätstrasse 1, D-40225, Düsseldorf, Germany.
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Nicholson C. Ion-selective microelectrodes and diffusion measurements as tools to explore the brain cell microenvironment. J Neurosci Methods 1993; 48:199-213. [PMID: 8412303 DOI: 10.1016/0165-0270(93)90092-6] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The construction and application of liquid-membrane ion-selective microelectrodes (ISM) are described. Recommendations are provided for the selection of appropriate cocktails containing neutral carriers to form the liquid membrane to sense K+, Ca2+, H+ and Na+. The use of charged carriers to sense Cl- and the cation tetramethylammonium (TMA+) is discussed. A detailed protocol is given for constructing double-barreled electrodes (ion-sensor and reference barrel) with tips of 1 micron diameter or more for extracellular ion measurements. The primary results obtained with ISMs in the brain cell microenvironment are briefly surveyed. The theoretical basis for measuring diffusion properties of extracellular space is described. Such measurements enable the estimation of volume fraction (proportion of tissue that is extracellular space) and tortuosity (hindrance of diffusion due to cellular obstructions). A method is given for using TMA+ ISMs in combination with iontophoresis or pressure ejection of TMA+ from a nearby micropipette to measure diffusion properties.
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Affiliation(s)
- C Nicholson
- Department of Physiology and Biophysics, New York University Medical Center, NY 10016
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Keicher E, Bilbaut A, Maggio K, Hernandez-Nicaise ML, Nicaise G. The Desheathed Periphery of Aplysia Giant Neuron. Fine Structure and Measurement of [Ca2+]o Fluctuations with Calcium-selective Microelectrodes. Eur J Neurosci 1991; 3:10-17. [PMID: 12106264 DOI: 10.1111/j.1460-9568.1991.tb00806.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The visceral ganglion of Aplysia was mechanically desheathed after protease softening of the connective tissue to permit the positioning of ion-selective electrodes in the vicinity of the neuronal membrane. The effects of this treatment on satellite glia and neuronal cytology were observed by electron microscopy. The intracellular alterations were not suggestive of serious membrane damage but the cohesion between glial and neuronal membranes was affected-the glial processes appeared to retract from the trophospongium and in some cases the neuronal membrane was completely naked. The external calcium activity [Ca2+]o at the surface of identified giant neuron, R2, was measured using double-barrelled calcium-selective microelectrodes. A decrease of approximately 1 mM in [Ca2+]o could be recorded only during trains of action potentials induced by intracellular depolarizing current injection, and when the electrode was pushed firmly against the neuron surface. A recovery from this decrease in [Ca2+]o could sometimes, but not always, be observed during the phase of induced neuronal activity.
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Affiliation(s)
- E. Keicher
- Laboratoire de Cytologie Expérimentale, Université de Nice-Sophia Antipolis, 06034 Nice, France
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De Graan PN, Schrama LH, Brussaard AB, Jork R, Gispen WH. 4-Aminopyridine affects synaptosomal protein phosphorylation in rat hippocampal slices. Brain Res 1987; 404:345-9. [PMID: 3032338 DOI: 10.1016/0006-8993(87)91392-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rat brain hippocampal slices were incubated with or without the convulsant 4-aminopyridine (4-AP). From these slices a crude mitochondrial/synaptosomal membrane fraction was prepared and analyzed for endogenous protein phosphorylation. 4-AP (10(-5) M) stimulated the phosphorylation of a 50 kDa protein by 86%. The phosphorylation of this 50 kDa protein is Ca2+/calmodulin-dependent and we suggest that this protein is the lower molecular weight subunit of Ca2+/calmodulin-dependent protein kinase II (CaMK II).
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Blaineau S, Julliard AK, Amsellem J, Nicaise G. Quantitative X-ray microanalysis of calcium with the Camebax-TEM system in frozen, freeze-substituted and resin-embedded tissue sections. Application to molluscan glio-interstitial granules. HISTOCHEMISTRY 1987; 87:545-55. [PMID: 3692921 DOI: 10.1007/bf00492469] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The relevance of the continuum method for a quantitative X-ray microanalysis of epon embedded tissue sections in the particular conditions offered by the Camebax-TEM system was tested and an improved model of specimen holder is proposed. The absolute calcium concentration [Ca] of membrane-bound intracellular glio-interstitial granules was determined by X-ray microanalysis in transmission electron microscopy of Mytilus retractor muscle. The Ca peak and background values were measured by the wavelength-dispersive spectrometer of the Camebax; the mass thickness of the section was recorded simultaneously with an added energy-dispersive detector. The tissue was frozen at approximately equal to 77 K in a mixture of liquid propane and butane, freeze-substituted in the presence of oxalic acid and embedded in epoxy resin. The calcium concentration of glio-interstitial granules can be as high as 180 mmol.kg-1 of epoxy-embedded tissue, with an average of 40 mmol.kg-1. The sampling of the data through repeated experiments is discussed and it is proposed that the cell would be the main level of variation. The Ca content of glio-interstitial granules is significantly lower in the tissues of animals submitted to high-potassium artificial sea-water for 10 min. This finding was predicted by the hypothesis that glio-interstitial tissue is a regulator of calcium concentration in extracellular spaces.
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Affiliation(s)
- S Blaineau
- Laboratoire de Physiologie des Elements Excitables, Université Claude Bernard, Villeurbanne, France
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Dubuc R, Rossignol S, Lamarre Y. The effects of 4-aminopyridine on the spinal cord: rhythmic discharges recorded from the peripheral nerves. Brain Res 1986; 369:243-59. [PMID: 3008935 DOI: 10.1016/0006-8993(86)90533-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of an intravenous injection (20 mg/kg) of 4-aminopyridine (4-AP) were initially investigated in acute low spinal cats (Th 13), in which L-DOPA had induced fictive locomotion after paralysis. 4-AP first accelerated the locomotor rhythm and could also change markedly the pattern of activation of some muscle nerves. Shortly after, the locomotor activity was replaced by synchronous rhythmic discharges (2.5-8.5 Hz) in flexor and extensor muscle nerves of the same limb girdle. Similar rhythmic activity was recorded after 4-AP alone (5-20 mg/kg) in the acute decerebrate spinal cat. Whilst the mean rate of the rhythmic activity could differ in the two limb girdles, discharges generated in one girdle appeared to be strongly influenced by those generated in the other. After a complete section of the spinal cord (Th13), the activity persisted in both the rostral and caudal segments although the interactions between the two disappeared. The persistence of the rhythmic activity caudal to the section underscores its spinal origin. In the chronic spinal rat, such rhythmic activity could still be induced in the lumbo-sacral cord despite degeneration of descending pathways. It appears that large doses of 4-AP exert potent effects on the spinal cord which can override other patterns of activity and synchronize the electrical activity of many neuronal elements.
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Schrama LH, De Graan PN, Wadman WJ, Lopes da Silva FH, Gispen WH. Long-term potentiation and 4-aminopyridine-induced changes in protein and lipid phosphorylation in the hippocampal slice. PROGRESS IN BRAIN RESEARCH 1986; 69:245-57. [PMID: 2833801 DOI: 10.1016/s0079-6123(08)61063-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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11
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Abstract
In addition to promoting long-lasting negative (and positive) dendritic field potentials elicited by stimulation of Schaffer collaterals in hippocampal slices, 4-aminopyridine causes a slow negative wave which may have another origin than the dendritic potentials.
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12
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Stokes BT, Hollinden G, Fox P. Improvement in injury induced hypocalcia by high-dose naloxone intervention. Brain Res 1984; 290:187-90. [PMID: 6692135 DOI: 10.1016/0006-8993(84)90753-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Naloxone hydrochloride was used to re-establish normal calcium activities in the extracellular space of the injured spinal cord. The micromolar levels of calcium which occur immediately after injury were improved above control values by 1 h 30 min post-injury; normal activities occurred at 2 h 45 min. Such a restitution of ionic levels after injury may contribute to the beneficial effects of naloxone in traumatic injury.
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13
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Abstract
The extracellular concentration of calcium ion was measured in canine spinal cord subsequent to spinal injury. In the control animal, we found that calcium activities changed little independent of electrode placement in the spinal cord, were stable during the 3 h necessary to make injury measurements, and were comparable to other estimates of calcium in the interstitial space. After injury, calcium activities decreased to micromolar levels that were incompatible with neural function. An incomplete recovery of extracellular calcium occurred during the next 3 h to about one-third (0.44 +/- 0.01 mM) of the normal value (1.1 +/- 0.08 mM). Such a pattern of changes in extracellular calcium was specific for the injury site itself and did not occur at nearby anatomic loci. These results are interpreted as having both short- and long-term effects on neuronal function and subsequent reorganization of spinal pathways.
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Ammann D, Morf W, Anker P, Meier P, Pretsch E, Simon W. Neutral Carrier Based Ion-Selective Electrodes. ION-SELECTIVE ELECTRODE REVIEWS 1983. [DOI: 10.1016/b978-0-08-031492-1.50005-x] [Citation(s) in RCA: 288] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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15
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Young W, Yen V, Blight A. Extracellular calcium ionic activity in experimental spinal cord contusion. Brain Res 1982; 253:105-13. [PMID: 6295546 DOI: 10.1016/0006-8993(82)90677-1] [Citation(s) in RCA: 164] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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16
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Parnas H, Segel LA. Ways to discern the presynaptic effect of drugs on neurotransmitter release. J Theor Biol 1982; 94:923-41. [PMID: 6122763 DOI: 10.1016/0022-5193(82)90087-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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17
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Critical evaluation of the applicability of neutral carrier-based calcium selective microelectrodes. Anal Chim Acta 1982. [DOI: 10.1016/s0003-2670(01)85264-8] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Szente M, Pongrácz F. Comparative study of aminopyridine-induced seizure activities in primary and mirror foci of cat's cortex. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1981; 52:353-67. [PMID: 6169512 DOI: 10.1016/0013-4694(81)90064-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Epileptogenic activity was induced by topical application of 3-Ap on the somatosensory cortex of anaesthetized cats. Surface epileptiform events were recorded and single cell activity was studied with intracellular electrodes both in the primary and in the mirror focus. Surface records showed that soon after the onset of paroxysmal activity in the primary focus, an epileptic mirror focus developed with variable delay. After MnCl2 treatment of the primary focus, the mirror focus generated independent epileptic events. In the primary and in the mirror focus 122 neurones were recorded intracellularly during seizure activity. Different firing patterns were observed. In the primary focus 31% and in the mirror focus 28% of the recorded neurones generated PDSs. The firing of the neurones in both foci was often phase-locked with surface waves. PDSs usually occurred asynchronously with the surface activity. Ionic mechanisms which may underlie the effect of 3-Ap are discussed.
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Kocsis JD, Malenka RC, Waxman SG. Enhanced parallel fiber frequency-following after reduction of postsynaptic activity. Brain Res 1981; 207:321-31. [PMID: 6258738 DOI: 10.1016/0006-8993(81)90367-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The frequency-following capabilities of the parallel fibers (Pf) of the rat cerebellar cortex were studied in the presence and absence of surround synaptic activity. When synaptic potentials were reduced or eliminated by local superfusion of the cerebellum with calcium antagonists or when they were reduced following a stimulation train, the Pfs showed more reliable frequency-following. Enhancement of synaptic activity with 4-aminopyridine (4-AP) application leads to a decrease in the frequency-following capabilities of the Pfs. When calcium antagonists were added to the 4-AP superfusate the synaptic enhancing effect of 4-AP was obliterated, and the Pfs displayed more reliable frequency-following capabilities. In addition, an extracellular slow potential was monitored and described in relation to the amplitude of the parallel fiber volley. We interpret these results to indicate that changes associated with postsynaptic activity of molecular layer neuronal elements may influence the frequency-following properties of presynaptic elements, i.e. the parallel fibers, possibly via an extracellular pathway.
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Pongrácz F, Szente M. On modelling the variability of interspike intervals during epileptic unit activity. BIOLOGICAL CYBERNETICS 1981; 41:165-177. [PMID: 7317517 DOI: 10.1007/bf00340318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In spite of the fact that the participation of well defined ionic particles in generating convulsive unit discharges is established, there is a gap between the data on ionic movements and on first-order statistics of firing patterns. Our aim was to tight this gap by studying the effectiveness of functionally separated electrical conductances of membrane during the generation of consecutive interspike interval histograms (IIHs) of unitary discharges. On account of the non-stationarity of the process curve fitting analysis which based on the simple modifications of the integrate-and-fire model has been implemented in the sequential interspike interval histogram procedure (SIIH). The experimental data were recorded from cat cortex treated with 3-Aminopyridine (3-Ap) by glass microelectrodes during nembutal anesthesia. Assuming the normal distribution of input parameters it is concluded, that the efficiency of the fluctuations of the active spike-generating conductance gg and the passive diffusional conductance gl may increase during the generation of the unimodal IIHs and the first mode of the bimodal IIHs. The simple conductance coupling gl=gg + b may participate in gg activation, moreover, the reciprocally coupled mechanism gg=c/gl may be driven by gl activation (a, b, c are the coupling constants). A temporal separation of processes governed by gg or gl respectively was observed. The time-independent occurrences of the reciprocally coupled conductance processes may be involved in the unit activities represented by the prolonged IIHs and second modes of the bimodal IIHs.
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Galvan M, Grafe P, ten Bruggencate G. Presynaptic actions of 4-aminopyridine and gamma-aminobutyric acid on rat sympathetic ganglia in vitro. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1980; 314:141-7. [PMID: 6256666 DOI: 10.1007/bf00504530] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Responses to bath-applications of 4-aminopyridine(4-AP) and gamma-aminobutyric acid (GABA) were recorded intracellularly from neurones in the rat isolated superior cervical ganglion. 4-aminopyridine (0.1-1.0 mmol/l) usually induced spontaneous action potentials and excitatory postsynaptic potentials (EPSPs), which were blocked by hexamethonium. Membrane potential was unchanged; spike duration was slightly increased. Vagus nerve B- and C-fibre potentials were prolonged. In 4-AP solution (0.2-0.3 mmol/l), GABA (0.1 mmol/l), 3-aminopropanesulphonic acid or muscimol evoked "bursts" of spikes and EPSPs in addition to a neuronal depolarization. These "bursts", which were not elicited by glycine, glutamate, taurine or (+/-)-baclofen, were completely antagonised by hexamethonium, tetrodotoxin or bicuculline methochloride. It is concluded that: (a) 4-AP has a potent presynaptic action on sympathetic ganglia; (b) presynaptic actions of GABA can be recorded postsynaptically in the presence of 4-AP; and (c) the presynaptic GABA-receptors revealed in this condition are similar to those on the postsynaptic membrane.
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Kocsis JD, Malenka RC, Waxman SG. Effects of 4-aminopyridine on the frequency following properties of the parallel fibers of the cerebellar cortex. Brain Res 1980; 195:511-6. [PMID: 6249447 DOI: 10.1016/0006-8993(80)90090-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Baranyi A, Fehér O. Convulsive effects of 3-aminopyridine on cortical neurones. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1979; 47:745-51. [PMID: 91505 DOI: 10.1016/0013-4694(79)90303-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The authors examined the effects of 3-aminopyridine (3-AP) on pyramidal tract neurones in the motor cortex of anesthetised cats. 3-AP proved to be a strong convulsive agent. Local application of 3-AP in concentrations of 15-20 mM resulted in typical paroxysmal alterations of neuronal activity: (a) enhancement of background firing, (b) augmentation of EPSPs, (c) depression of IPSPs and (d) single and serial paroxysmal depolarization shifts (PDSs). Serial PDSs were reflected by large synchronous waves in the surface ECoG.
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Tokunaga A, Sandri C, Akert K. Increase of large intramembranous particles in the presynaptic active zone after administration of 4-aminopyridine. Brain Res 1979; 174:207-19. [PMID: 487127 DOI: 10.1016/0006-8993(79)90845-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The effects of 4-aminopyridine (4-AP, 1 mg/kg i.v.) on the distribution of intramembranous particles in spinal motoneuronal synapses was examined in anesthetized (pentobarbital sodium, 50 mg/kg, i.p.) rats by freeze-etching electron microscopy. The particles were classified according to their size into small (4.2--10.5 nm in diameter) and large (10.5--18.9 nm in diameter). The active zone of the presynaptic membrane was identified on the basis of ultrastructural criteria. The large intramembranous particles in both protoplasmic (PF) and external fracture faces (EF) were aggregated more densely in the active zone as compared with its surroundings both in the control and 4-AP-treated group (P less than 0.001). The density of large particles in the PF rose from 300/sq.micron under the influence of 4-AP (P less than 0.001). The increased frequency of vesicle attachment sites at the presynaptic membrane (from 115/sq.micron in barbiturized controls to 150/sq.micron in 4-AP treated animals) seemed to be positively correlated with the increasing density of large particles. Based on these findings it is suggested that the large intramembranous particles of the presynaptic membrane may participate in the control of calcium fluxes which are essential to the transmitter release by exocytosis.
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Szente M, Pongrácz F. Aminopyridine-induced seizure activity. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1979; 46:605-8. [PMID: 88349 DOI: 10.1016/0013-4694(79)90014-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Typical seizure activity can be induced by applying 3-aminopyridine to the surface of the cat cortex. The well known characteristics of epileptiform discharges were readily observed by simultaneous recording from both the surface and deeper layers.
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Folgering H, Rutten J, Agoston S. Stimulation of phrenic nerve activity by an acetylcholine releasing drug: 4-aminopyridine. Pflugers Arch 1979; 379:181-5. [PMID: 571113 DOI: 10.1007/bf00586945] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The effect of the acetylcholine releaser 4-aminopyridine on ventilation was studied by recording and quantifying the efferent phrenic nerve activity in 40 paralysed and vagotomized cats; with arterial Po2, PCO2 and pH kept constant. 4-Aminopyridine, given intravenously or in the vertebral artery, stimulates the phrenic nerve activity in a dose dependent manner. The stimulatory effects of 4-aminopyridine on the phrenic nerve activity could be abolished completely by administration of high doses of atropine. We conclude that 4-aminopyridine, which is used clinically for the reversal of a neuromuscular block, stimulates the phrenic nerve activity. Since the role of cholinergic mechanisms in the central chemoreception has been well established, the effect on the phrenic nerve activity is most probably by an increased release of acetylcholine at the site of the central chemoreceptors.
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Tokunaga A, Sandri C, Akert K. Ultrastructural effects of 4-aminopyridine on the presynaptic membrane in the rat spinal cord. Brain Res 1979; 163:1-8. [PMID: 427535 DOI: 10.1016/0006-8993(79)90146-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The effects of 4-aminopyridine (4-AP, 1 mg/kg, i.v.) on the ultrastructure of synapses in the ventral horn of the spinal cord were examined in rats anesthetized with 50 and 100 mg/kg, i.p., pentobarbital sodium and alpha-chloralose respectively. The presynaptic membrane of the 4-AP-treated animals, in both S- and F-type synapses, was wrinkled and gave frequently rise to omega-shaped profiles. However, it was not prominently lifted in comparison with the controls. In both extracellular (EF) and protoplasmic fracture faces (PF) of freeze-etched replicas, the frequency of the presynaptic membrane modulations (PMM) per unit area rose significantly under the influence of 4-AP. The ratio of open (crater-like) to total PMM in EF increased almost twice under the experimental condition. No differential 4-AP effects were seen between pentobarbital- and chloralose-treated animals. The morphological evidence is consistent with electrophysiological data showing that 4-AP facilitates the transmitter release at synaptic endings.
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Galvan M, Bruggencate GT, Senekowitsch R. The effects of neuronal stimulation and ouabain upon extracellular K+ and Ca2+ levels in rat isolated sympathetic ganglia. Brain Res 1979; 160:544-8. [PMID: 217484 DOI: 10.1016/0006-8993(79)91084-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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