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Elis F Stanley - One of the best experts on this subject based on the ideXlab platform.
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g protein types involved in calcium channel inhibition at a Presynaptic Nerve terminal
The Journal of Neuroscience, 2000Co-Authors: Rukmini R Mirotznik, Xu Zheng, Elis F StanleyAbstract:The inhibition of Presynaptic calcium channels via G-protein-dependent second messenger pathways is a key mechanism of transmitter release modulation. We used the calyx-type Nerve terminal of the chick ciliary ganglion to examine which G-proteins are involved in the voltage-sensitive inhibition of Presynaptic N-type calcium channels. Adenosine caused a prominent inhibition of the calcium current that was totally blocked by pretreatment with pertussis toxin (PTX), consistent with an exclusive involvement of Go/Gi in the G-protein pathway. Immunocytochemistry was used to localize these G-protein types to the Nerve terminal and its transmitter release face. We used two approaches to test for modulation by other G-protein types. First, we treated the terminals with ligands for a variety of G-protein-linked neurotransmitter receptor types that have been associated with different G-protein families. Although small inhibitory effects were observed, these could all be eliminated by PTX, indicating that in this terminal the Gi family is the sole transmitter-induced G-protein inhibitory pathway. Second, we examined the kinetics of calcium channel inhibition by uncaging the nonselective and irreversible G-protein activator GTPγS, bypassing the receptors. A large fraction of the rapid GTPγS-induced inhibition persisted, consistent with a Go/Gi-independent pathway. Immunocytochemistry identified Gq, G11, G12, and G13 as potential PTX-insensitive second messengers at this terminal. Thus, our results suggest that whereas neurotransmitter-mediated calcium channel inhibition is mainly, and possibly exclusively, via Go/Gi, other rapid PTX-insensitive G-protein pathways exist that may involve novel, and perhaps transmitter-independent, activating mechanisms.
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Presynaptic calcium channels and the depletion of synaptic cleft calcium ions
Journal of Neurophysiology, 2000Co-Authors: Elis F StanleyAbstract:The entry of calcium ions (Ca2+) through voltage-gated calcium channels is an essential step in the release of neurotransmitter at the Presynaptic Nerve terminal. Because the calcium channels are c...
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single channel properties of bk type calcium activated potassium channels at a cholinergic Presynaptic Nerve terminal
The Journal of Physiology, 1999Co-Authors: Xiao Ping Sun, Lyanne C Schlichter, Elis F StanleyAbstract:Substantial evidence suggests that most, if not all, Nerve terminals that secrete neurotransmitters by action potential-dependent mechanisms exhibit a calcium-activated potassium (KCa) channel. Such terminals include Presynaptic Nerve terminals at fast-transmitting synapses (Bartschat & Blaustein, 1985; Farley & Rudy, 1988; Anderson et al. 1988; Lindgren & Moore, 1989; Schneider et al. 1989; Astrand & Stjarne, 1991; Sivaramakrishnan et al. 1991; Robitaille & Charlton, 1992; Wangemann & Takeuchi, 1993; Blundon et al. 1995; Rahamimoff et al. 1995; Katz et al. 1997; Sakaba et al. 1997; Yazejian et al. 1997), hormone-secreting Nerve terminals (Bielefeldt et al. 1992; Wang & Lemos, 1992; Wang et al. 1992; Bielefeldt & Jackson, 1993) and sense-organ cells (such as hair cells, Edgington & Stewart, 1981; Roberts et al. 1990, 1991; Issa & Hudspeth, 1994; Art et al. 1995) which share many properties with fast-transmitting Nerve terminals. It is not clear which specific types of KCa channel are present at most of these sites but, where tested by specific staining or direct recording, the high-conductance, BK-type has been repeatedly observed (Smith et al. 1986; Castle & Strong, 1986; Roberts et al. 1991; Robitaille & Charlton, 1992; Bielefeldt & Jackson, 1993; Wangemann & Takeuchi, 1993; Issa & Hudspeth, 1994; Art et al. 1995; Knaus et al. 1996). Other studies have presented more indirect evidence for the presence of this channel in the Nerve terminal on the basis of effects of peptide blockers, primarily charybdotoxin (CTX) or iberiotoxin (IbTX), or intracellular buffers on transmitter release (Kumamoto & Kuba, 1985; Sivaramakrishnan et al. 1991; Robitaille & Charlton, 1992; Stretton et al. 1992; Takeuchi & Wangemann, 1993; Robitaille et al. 1993; Yazejian et al. 1997). Despite the evident broad distribution of BK channels in Nerve terminals little is known about their biophysical properties and to what extent these may differ from their relatives in the cell soma. This question has become of particular interest recently with the discovery that the BK channel can be expressed in many functionally different isoforms (Butler et al. 1993; Wei et al. 1998). In addition, the channel can associate with a β subunit (Vergara et al. 1998) that has marked effects on its biophysical and pharmacological properties. Thus, because of this diversity a full understanding of the role of this channel in the Nerve terminal requires direct recording of its properties in situ. Furthermore, the complex activation characteristics of the BK channel require analysis at the single-channel level since it is gated by both a ligand and a physical factor, i.e. calcium and voltage. There have been only two Nerve terminals at which the single-channel properties of BK channels have been examined (Wang et al. 1992; Wangemann & Takeuchi, 1993; Bielefeldt & Jackson, 1993) due, presumably, to the general small size and inaccessibility of these structures. Few Nerve terminals are of sufficiently large size to permit direct patch-clamp recording, and in the cases where this is possible obtaining sufficient data requires considerable experimental effort. This study presents the first characterization of single BK channels at the Presynaptic Nerve terminal of a neuron-to-neuron synapse. We used the calyx-type synapse of the chick ciliary ganglion (CCG) to record and characterize single Presynaptic high-conductance KCa channels. This experimental preparation was the first in which an intact vertebrate Presynaptic terminal could be voltage clamped to record whole-terminal currents (Stanley, 1989) or clamped in the cell-attached configuration (Stanley, 1991) to record single-channel activity. We have recently presented evidence for the presence of KCa channels on this terminal by direct recording of an outwardly rectifying K+ current that was sensitive to CTX and IbTX (Tozer et al. 1998). In this study we first used the patch-clamp technique in the outside-out and inside-out configurations to test for block with standard K+ channel blockers. We next used the same techniques to examine the voltage and calcium sensitivity of single BK channels. Finally, we used the cell-attached configuration to test whether Presynaptic BK channels could be activated by calcium influx through the same membrane patch.
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an atp activated ligand gated ion channel on a cholinergic Presynaptic Nerve terminal
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Xiao Ping Sun, Elis F StanleyAbstract:Abstract ATP has recently been identified as a fast neurotransmitter in both the central and peripheral nervous systems. Several studies have suggested that ATP can also affect the release of classical neurotransmitters, including acetylcholine with which it is co-released. We have searched for ATP receptors on a cholinergic Presynaptic Nerve terminal using the calyx-type synapse of the chicken ciliary ganglion. ATP was pulsed onto the terminals under voltage clamp and induced a short latency cation current that exhibited inward rectification and marked desensitization. This current was not seen with adenosine but was mimicked by several sterically restricted ATP analogs and was blocked by suramin. ATP-activated single ion channels exhibited prominent flickering and had a conductance of approximately 17 pS. Our results demonstrate a ligand-gated P2X-like purinergic receptor on a cholinergic Presynaptic Nerve terminal.
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localization of individual calcium channels at the release face of a Presynaptic Nerve terminal
Neuron, 1994Co-Authors: Philip G Haydon, Eric Henderson, Elis F StanleyAbstract:Summary Studies using biophysical techniques suggest a highly structured organization of calcium channels at the Presynaptic transmitter release face (Llinas et al., 1981; Stanley, 1993), but it has not as yet proved possible to localize identified channels at the required nanometer level of resolution. We have used atomic force microscopy on the calyx-type Nerve terminal of the chick ciliary ganglion to localize single calcium channels tagged via biotinylated ω-conotoxin GVIA to avidin-coated 30 nm gold particles. Calcium channels were in low (modal value approximately ⩽ 1 per μm 2 ) and high (modal value55 per μm 2 ) density areas and exhibited a prominent interchannel spacing of 40 nm, indicating an intermolecular linkage. Particles were observed in clusters and short linear or parallel linear arrays, groupings that may reflect calcium channel organization at the transmitter release site.
Norio Akaike - One of the best experts on this subject based on the ideXlab platform.
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effects of ethanol on gabaa receptors in gabaergic and glutamatergic Presynaptic Nerve terminals
Journal of Pharmacology and Experimental Therapeutics, 2012Co-Authors: Masahito Wakita, Min Chul Shin, Satomi Iwata, Kiku Nonaka, Norio AkaikeAbstract:Ethanol (EtOH) has a number of behavioral effects, including intoxication, amnesia, and/or sedation, that are thought to relate to the activation of GABAA receptors. However, GABAA receptors at different cellular locations have different sensitivities to EtOH. The present study used the “synaptic bouton” preparation where we could stimulate Nerve endings on mechanically dissociated single rat hippocampal CA1 and CA3 pyramidal neurons and investigate the effects of EtOH on Presynaptic and postsynaptic GABAA receptors. Low concentrations of EtOH (10 mM) had no effect on postsynaptic GABAA and glutamate receptors or voltage-dependent Na+ and Ca2+ channels. Higher concentrations (≥100 mM) could significantly inhibit these current responses. EtOH at 10 mM had no direct effect on inhibitory postsynaptic currents (IPSCs) and excitatory postsynaptic currents (EPSCs) evoked by focal stimulation of single boutons [evoked IPSCs (eIPSCs) and evoked EPSCs (eEPSCs)]. However, coapplication of 10 mM EtOH with muscimol decreased the amplitude of eIPSCs and eEPSCs and increased their paired-pulse ratio. The effects on eEPSCs were reversed by bicuculline. Coapplication of muscimol and EtOH significantly increased the frequency of spontaneous IPSCs and EPSCs. The EtOH effects on the postsynaptic responses and eEPSCs were similar in neurons from neonatal and mature rats. These results revealed that low concentrations of EtOH can potentiate the activation of Presynaptic GABAA receptors to inhibit evoked GABA and glutamate release. These results indicate a high sensitivity of Presynaptic GABAA receptor to EtOH, which needs to be accounted for when considering the cellular mechanisms of EtOH's physiological responses.
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the na h exchanger is a major ph regulator in gabaergic Presynaptic Nerve terminals synapsing onto rat ca3 pyramidal neurons
Journal of Neurochemistry, 2006Co-Authors: Il-sung Jang, Hyo-jin Jeong, Malcolm S Brodwick, Zhi Ming Wang, Byungju Choi, Norio AkaikeAbstract:The effects of pHi on GABAergic miniature inhibitory postsynaptic currents (mIPSCs) were studied in mechanically dissociated CA3 pyramidal neurons, by use of ammonium prepulse and whole-cell patch-clamp techniques, under the voltage-clamp condition. NH4Cl itself, which is expected to alkalinize pHi, increased GABAergic mIPSC frequency in a concentration-dependent manner. In contrast, NH4Cl decreased mIPSC frequency, either in the presence of 200 µm Cd2+ or in Ca2+-free external solution, suggesting that intraterminal alkalosis decreased GABAergic mIPSC frequency while [NH4+] itself may activate Ca2+ channels by depolarizing the terminal. On the other hand, GABAergic mIPSC frequency was greatly increased immediately after NH4Cl removal, a condition expected to acidify pHi, and recovered to the control level within 2 min after NH4Cl removal. This explosive increase in mIPSC frequency observed after NH4Cl removal was completely eliminated after depletion of Ca2+ stores with 1 µm thapsigargin in the Ca2+-free external solution, suggesting that acidification increases in intraterminal Ca2+ concentration via both extracellular Ca2+ influx and Ca2+ release from the stores. However, the acidification-induced increase in mIPSC frequency had not recovered by 10 min after NH4Cl removal either in the Na+-free external solution or in the presence of 10 µm 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), a specific Na+/H+ exchanger (NHE) blocker. The present results suggest that NHEs are major intraterminal pH regulators on GABAergic Presynaptic Nerve terminals, and that the NHE-mediated regulation of pHi under normal physiological or pathological conditions might play an important role in the neuronal excitability by increasing inhibitory tones.
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inhibitory effects of 1 4 dhp antagonists on synaptic gaba release modulated by bay k 8644 in mechanically dissociated rat substantia innominata
Life Sciences, 2002Co-Authors: Yasuo Watanabe, Hitoshi Ishibashi, Jeong-seop Rhee, Zhi Ming Wang, George F Lawlor, Norio AkaikeAbstract:Abstract The effects of dihydropyridine (1,4-DHP) agonist and antagonists on miniature inhibitory postsynaptic currents (mIPSCs) were investigated in mechanically dissociated rat substantia innominata neurons attached to native GABAergic Presynaptic Nerve terminals, namely ‘synaptic bouton preparation’, using nystatin perforated patch recording mode under voltage-clamp conditions. BAY-K 8644 (BAY-K), an L-type Ca 2+ channel agonist, reversibly and concentration dependently facilitated the GABAergic mIPSC frequency without altering the distribution of current amplitudes. Removal of extracellular Ca 2+ completely suppressed the facilitatory effect of BAY-K on mIPSC frequency. The facilitatory effect of BAY-K on mIPSC frequency was maintained even in the presence of selective N-, P- and Q-type Ca 2+ channel antagonists, such as 3 × 10 −6 M ω-conotoxin-GVIA (ω-CgTX-GVIA), 3 × 10 −8 M ω-agatoxin-IVA (ω-AgTX-IVA) and 3 × 10 −6 M ω-conotoxin-MVIIC (ω-CmTX-MVIIC). However, nicardipine (3 × 10 −6 M) and nimodipine (3 × 10 −6 M), 1,4-DHP antagonists, significantly inhibited the mIPSC frequency enhanced by BAY-K by 37 ± 5 and 42 ± 6%, respectively. These results suggest the possible existence of L-type Ca 2+ channels in GABAergic Presynaptic Nerve terminals.
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developmental changes in p2x purinoceptors on glycinergic Presynaptic Nerve terminals projecting to rat substantia gelatinosa neurones
The Journal of Physiology, 2001Co-Authors: Il-sung Jang, Jeong-seop Rhee, Hisahiko Kubota, Norihiko Akaike, Norio AkaikeAbstract:1. In mechanically dissociated rat spinal cord substantia gelatinosa (SG) neurones attached with native Presynaptic Nerve endings, glycinergic miniature inhibitory postsynaptic currents (mIPSCs) were recorded using nystatin perforated patch recording mode under voltage-clamp conditions. Under these conditions, it was tested whether the changes in P2X receptor subtype on the glycinergic Presynaptic Nerve terminals occur during postnatal development. 2. ATP facilitated glycinergic mIPSC frequency in a concentration-dependent manner through all developmental stages tested, whereas alphabeta-methylene-ATP (alphabeta-me-ATP) was only effective at later developmental stages. 3. alphabeta-me-ATP-elicited mIPSC frequency facilitation was completely occluded in the Ca2+-free external solution, but it was not affected by adding 10(-4) M Cd2+. 4. alphabeta-me-ATP still facilitated mIPSC frequency even in the presence of 10(-6) M thapsigargin, a Ca2+ pump blocker. 5. In later developmental stages, ATP-elicited Presynaptic or postsynaptic responses were reversibly blocked by 10(-5) M pyridoxal-5-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), but only partially blocked by 10(-7) M 2',3'-O-(2,4,6-trinitrophenyl)-ATP (TNP-ATP). However, alphabeta-me-ATP-elicited Presynaptic or postsynaptic responses were completely and reversibly blocked by either 10(-5) M PPADS or 10(-7) M TNP-ATP. 6. alphabeta-me-ATP significantly reduced the evoked glycinergic IPSC amplitude in postnatal 28-30 day neurones, whereas it had no effect in 10-12 day neurones. 7. It was concluded that alphabeta-me-ATP-sensitive P2X receptors were functionally expressed on the glycinergic Presynaptic Nerve terminals projecting to SG neurones in later developmental stages. Such developmental changes of Presynaptic P2X receptor subtypes might contribute to synaptic plasticity such as the regulation of neuronal excitability and the fine controlling of the pain signal in spinal dorsal horn neurones.
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Contribution of the Na-K-Cl cotransporter on GABA(A) receptor-mediated Presynaptic depolarization in excitatory Nerve terminals.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2001Co-Authors: Il-sung Jang, Hyo-jin Jeong, Norio AkaikeAbstract:GABAA receptor-mediated responses manifest as either hyperpolarization or depolarization according to the intracellular Cl− concentration ([Cl−]i). Here, we report a novel functional interaction between the Na–K–Cl cotransporter (NKCC) and GABAA receptor actions on glutamatergic Presynaptic Nerve terminals projecting to ventromedial hypothalamic (VMH) neurons. The activation of Presynaptic GABAA receptors depolarizes the Presynaptic Nerve terminals and facilitates spontaneous glutamate release by activating TTX-sensitive Na+ channels and high-threshold Ca2+ channels. This depolarizing action of GABA was caused by an outwardly directed Cl− driving force for GABAA receptors; that is, the [Cl−]i of glutamatergic Nerve terminals was higher than that predicted for a passive distribution. The higher [Cl−]i was generated by bumetanide-sensitive NKCCs and was responsible for the GABA-induced Presynaptic depolarization. Thus, GABAAreceptor-mediated modulation of spontaneous glutamatergic transmission may contribute to the development and regulation of VMH function as well as to the excitability of VMH neurons themselves.
Elise F Stanley - One of the best experts on this subject based on the ideXlab platform.
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the calcium channel and the organization of the Presynaptic transmitter release face
Trends in Neurosciences, 1997Co-Authors: Elise F StanleyAbstract:Abstract Calcium influx through ion channels located on the release face of the Presynaptic Nerve terminal gates the release of neurotransmitters by the fusion of the secretory vesicle and the discharge of its contents. Recently, several lines of research have indicated that the relationship between the Ca 2+ channel and the release site might be more complex than dictated simply by its role as an ion conduit. The evidence suggests that the channel and the transmitter-release mechanism exist as a multimolecular entity and that this interaction has functional consequences, not only on the mechanism and properties of transmitter release, but also on the behavior of the Presynaptic Ca 2+ channel itself.
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single calcium channels and acetylcholine release at a Presynaptic Nerve terminal
Neuron, 1993Co-Authors: Elise F StanleyAbstract:The relationship between calcium influx and the gating of transmitter release was examined at the release face of a cholinergic Presynaptic Nerve terminal using a technique that allows the simultaneous recording of both calcium channels at the single-channel level and quantal acetylcholine secretion. Acetylcholine release occurred during large inward calcium currents through many simultaneously open channels but was also gated by very small calcium transients, admitting less than 200 ions, when only one channel was open at a time. These findings provide functional support for a highly structured model of the transmitter release face in which the synaptic vesicle release mechanism is closely tethered to one or more Presynaptic calcium channels and the opening of only one of these may be sufficient to trigger quantal secretion.
Richard H. Scheller - One of the best experts on this subject based on the ideXlab platform.
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synaptic vesicle biogenesis docking and fusion a molecular description
Physiological Reviews, 1996Co-Authors: Nicole Calakos, Richard H. SchellerAbstract:Secretion of neurotransmitter is the primary means of intercellular communication within the nervous system. This process is regulated by a highly orchestrated cycle of membrane trafficking within the Presynaptic Nerve terminal. Characterization of proteins localized to the synaptic vesicle and the subsequent studies of their properties have led to a model for the biochemical pathway that underlies vesicle docking, activation, and fusion. The proteins found to function in the synapse are related to those in yeast and other organisms, demonstrating that the mechanisms that mediate vesicle trafficking are conserved in all eukaryotic species.
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cellular and molecular biology of the Presynaptic Nerve terminal
Annual Review of Neuroscience, 1991Co-Authors: William S Trimble, Michal Linial, Richard H. SchellerAbstract:Chemical neurotransmission represents the primary form of intercellular communication in the nervous system, yet relatively little is known about the molecular processes involved. The vesicle hypothesis states that spe cialized organelles located in the synaptic region are responsible for the accumulation, storage, and release of neurotransmitters in discrete packets called "quanta." These synaptic vesicles, or their components, are thought to be assembled in the cell body and transported to the terminals via fast axonal transport. At the Nerve terminal, vesicles interact with the cytoskeleton and with soluble vesicle-binding proteins prior to docking at specialized membrane sites known as active zones. Following voltage gated Ca 2+ influx, when the local intracellular Ca 2+ concentrations ([Ca 2+]i) may reach several hundred micromolar, the vesicle and the plasma membrane fuse, releasing the vesicle contents into the synaptic cleft. A typical synaptic vesicle from a motoneuron releases approximately 5000 molecules of acetylcholine, and each Nerve impulse releases 100-200 quanta at a representative neuromuscular synapse. Following exocytosis,
Rami Rahamimoff - One of the best experts on this subject based on the ideXlab platform.
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ion channels in Presynaptic Nerve terminals and control of transmitter release
Physical Review, 1999Co-Authors: Alon Meir, Simona Ginsburg, Alexander Butkevich, Sylvia G Kachalsky, Igor Kaiserman, Ronit Ahdut, Serdar Demirgoren, Rami RahamimoffAbstract:The primary function of the Presynaptic Nerve terminal is to release transmitter quanta and thus activate the postsynaptic target cell. In almost every step leading to the release of transmitter qu...
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ion channels in Presynaptic Nerve terminals and control of transmitter release
Physical Review, 1999Co-Authors: Alon Meir, Simona Ginsburg, Alexander Butkevich, Sylvia G Kachalsky, Igor Kaiserman, Ronit Ahdut, Serdar Demirgoren, Rami RahamimoffAbstract:The primary function of the Presynaptic Nerve terminal is to release transmitter quanta and thus activate the postsynaptic target cell. In almost every step leading to the release of transmitter quanta, there is a substantial involvement of ion channels. In this review, the multitude of ion channels in the Presynaptic terminal are surveyed. There are at least 12 different major categories of ion channels representing several tens of different ion channel types; the number of different ion channel molecules at Presynaptic Nerve terminals is many hundreds. We describe the different ion channel molecules at the surface membrane and inside the Nerve terminal in the context of their possible role in the process of transmitter release. Frequently, a number of different ion channel molecules, with the same basic function, are present at the same Nerve terminal. This is especially evident in the cases of calcium channels and potassium channels. This abundance of ion channels allows for a physiological and pharmacological fine tuning of the process of transmitter release and thus of synaptic transmission.