scholarly journals α7-nAChR agonist enhances neural plasticity in the hippocampus via a GABAergic circuit

2016 ◽  
Vol 116 (6) ◽  
pp. 2663-2675 ◽  
Author(s):  
Matthew Townsend ◽  
Andrew Whyment ◽  
Jean-Sebastien Walczak ◽  
Ross Jeggo ◽  
Marco van den Top ◽  
...  
Keyword(s):  
Neural Plasticity ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Α7 Nachr ◽  
Term Potentiation ◽  
Functional Outcome Measures ◽  
Gabaergic Activity ◽  
Whole Cell Recordings

Agonists of the α7-nicotinic acetylcholine receptor (α7-nAChR) have entered clinical trials as procognitive agents for treating schizophrenia and Alzheimer's disease. The most advanced compounds are orthosteric agonists, which occupy the ligand binding site. At the molecular level, agonist activation of α7-nAChR is reasonably well understood. However, the consequences of activating α7-nAChRs on neural circuits underlying cognition remain elusive. Here we report that an α7-nAChR agonist (FRM-17848) enhances long-term potentiation (LTP) in rat septo-hippocampal slices far below the cellular EC50 but at a concentration that coincides with multiple functional outcome measures as we reported in Stoiljkovic M, Leventhal L, Chen A, Chen T, Driscoll R, Flood D, Hodgdon H, Hurst R, Nagy D, Piser T, Tang C, Townsend M, Tu Z, Bertrand D, Koenig G, Hajós M. Biochem Pharmacol 97: 576–589, 2015. In this same concentration range, we observed a significant increase in spontaneous γ-aminobutyric acid (GABA) inhibitory postsynaptic currents and a moderate suppression of excitability in whole cell recordings from rat CA1 pyramidal neurons. This modulation of GABAergic activity is necessary for the LTP-enhancing effects of FRM-17848, since inhibiting GABAA α5-subunit-containing receptors fully reversed the effects of the α7-nAChR agonist. These data suggest that α7-nAChR agonists may increase synaptic plasticity in hippocampal slices, at least in part, through a circuit-level enhancement of a specific subtype of GABAergic receptor.

scholarly journals GPR68 deletion impairs hippocampal long-term potentiation and passive avoidance behavior

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Yuanyuan Xu ◽  
Mike T. Lin ◽  
Xiang-ming Zha
Keyword(s):  
Passive Avoidance ◽  
Pyramidal Neurons ◽  
Granule Cells ◽  
Hippocampal Slices ◽  
Synaptic Cleft ◽  
Long Term Potentiation ◽  
Synaptic Function ◽  
Metabotropic Receptor ◽  
Term Potentiation

Abstract Increased neural activities reduced pH at the synaptic cleft and interstitial spaces. Recent studies have shown that protons function as a neurotransmitter. However, it remains unclear whether protons signal through a metabotropic receptor to regulate synaptic function. Here, we showed that GPR68, a proton-sensitive GPCR, exhibited wide expression in the hippocampus, with higher expression observed in CA3 pyramidal neurons and dentate granule cells. In organotypic hippocampal slice neurons, ectopically expressed GPR68-GFP was present in dendrites, dendritic spines, and axons. Recordings in hippocampal slices isolated from GPR68−/− mice showed a reduced fiber volley at the Schaffer collateral-CA1 synapses, a reduced long-term potentiation (LTP), but unaltered paired-pulse ratio. In a step-through passive avoidance test, GPR68−/− mice exhibited reduced avoidance to the dark chamber. These findings showed that GPR68 contributes to hippocampal LTP and aversive fear memory.

Sleep Deprivation Impairs Long-Term Potentiation in Rat Hippocampal Slices

2002 ◽  
Vol 88 (2) ◽  
pp. 1073-1076 ◽  
Author(s):  
I. G. Campbell ◽  
M. J. Guinan ◽  
J. M. Horowitz
Keyword(s):  
Sleep Deprivation ◽  
Neural Plasticity ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Adult Rats ◽  
Cellular Processes ◽  
Term Potentiation ◽  
Population Spike Amplitude ◽  
Specific Factors

To determine if 12-h sleep deprivation disrupts neural plasticity, we compared long-term potentiation (LTP) in five sleep-deprived and five control rats. Thirty minutes after tetanus population spike amplitude increased 101 ± 15% in 16 slices from sleep deprived rats and 139 ± 14% in 14 slices from control rats. This significant ( P < 0.05) reduction of LTP, the first demonstration that the sleep deprivation protocol impairs plasticity in adult rats, may be due to several factors. Reduced LTP may indicate that sleep provides a period of recuperation for cellular processes underlying neural plasticity. Alternatively, the stress of sleep deprivation, as indicated by elevated blood corticosterone levels, or other non-sleep-specific factors of deprivation may contribute to the LTP reduction.

Intraneuronal [Ca2+] Changes Induced by 2-Deoxy-d-Glucose in Rat Hippocampal Slices

1999 ◽  
Vol 81 (1) ◽  
pp. 174-183 ◽  
Author(s):  
S. Tekkök ◽  
I. Medina ◽  
K. Krnjević
Keyword(s):  
Wistar Rats ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Synergistic Action ◽  
Tetraacetic Acid ◽  
Term Potentiation ◽  
The One ◽  
Peak Increase

Tekkök, S., I. Medina, and K. Krnjević. Intraneuronal [Ca2+] changes induced by 2-deoxy-d-glucose in rat hippocampal slices. J. Neurophysiol. 81: 174–183, 1999. Temporary replacement of glucose by 2-deoxyglucose (2-DG; but not sucrose) is followed by long-term potentiation of CA1 synaptic transmission (2-DG LTP), which is Ca2+-dependent and is prevented by dantrolene or N-methyl-d-aspartate (NMDA) antagonists. To clarify the mechanism of action of 2-DG, we monitored [Ca2+]i while replacing glucose with 2-DG or sucrose. In slices (from Wistar rats) kept submerged at 30°C, pyramidal neurons were loaded with [Ca2+]-sensitive fluo-3 or Fura Red. The fluorescence was measured with a confocal microscope. Bath applications of 10 mM 2-DG (replacing glucose for 15 ± 0.38 min, means ± SE) led to a rapid but reversible rise in fluo-3 fluorescence (or drop of Fura Red fluorescence); the peak increase of fluo-3 fluorescence (Δ F/ F 0), measured near the end of 2-DG applications, was by 245 ± 50% ( n = 32). Isosmolar sucrose (for 15–40 min) had a smaller but significant effect (Δ F/ F 0 = 94 ± 14%, n = 10). The 2-DG–induced Δ F/ F 0 was greatly reduced (to 35 ± 15%, n = 16) by d,l-aminophosphono-valerate (50–100 μM) and abolished by 10 μM dantrolene (−4.0 ± 2.9%, n = 11). A substantial, although smaller effect, of 2-DG persisted in Ca2+-free 1 mM ethylene glycol-bis(β-aminoethyl ether)- N, N, N′, N′-tetraacetic acid (EGTA) medium. Two adenosine antagonists, which do not prevent 2-DG LTP, were also tested; 2-DG–induced Δ F/ F 0 (fluo-3) was not affected by the A1 antagonist 8-cyclopentyl-3,7-dihydro-1,3-dipropyl-1H-purine-2,6-dione (DPCPX 50 nM; 287 ± 38%; n = 20), but it was abolished by the A1/A2 antagonist 8-SPT; 25 ± 29%, n = 19). These observations suggest that 2-DG releases glutamate and adenosine and that the rise in [Ca2+] may be triggered by a synergistic action of glutamate (acting via NMDA receptors) and adenosine (acting via A2b receptors) resulting in Ca2+ release from a dantrolene-sensitive store. The discrepant effects of sucrose and 8-SPT on Δ F/ F 0, on the one hand, and 2-DG LTP, on the other, support other evidence that increases in postsynaptic [Ca2+]i are not essential for 2-DG LTP.

The involvement of nonspiking cells in long-term potentiation of synaptic transmission in the hippocampus

1988 ◽  
Vol 66 (6) ◽  
pp. 841-844 ◽  
Author(s):  
B. R. Sastry ◽  
J. W. Goh ◽  
P. B. Y. May ◽  
S. S. Chirwa
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Stratum Radiatum ◽  
Ca1 Pyramidal Neurons ◽  
Term Potentiation ◽  
Ca1 Area ◽  
Glial Depolarization ◽  
Stimulation Of

In guinea pig hippocampal slices, stimulation of stratum radiatum during depolarization (with intracellular current injections) of nonspiking cells (presumed to be glia) in the apical dendritic area of CA1 pyramidal neurons resulted in a subsequent long-term potentiation of intracellularly recorded excitatory postsynaptic potentials as well as extracellularly recorded population spikes in the CA1 area. Tetanic stimulation of stratum radiatum resulted in a subsequent prolonged depolarization of the presumed glial cells, and this depolarization was smaller when the tetanus was given during the presence of 2-amino-5-phosphonovalerate or when the slices were exposed to Ca2+-free medium containing Mn2+ and Mg2+. These results suggest that glial depolarization is involved as one of the steps in generating long-term potentiation.

Quantal mechanism of long-term potentiation in hippocampal mossy-fiber synapses

1994 ◽  
Vol 71 (6) ◽  
pp. 2552-2556 ◽  
Author(s):  
Z. Xiang ◽  
A. C. Greenwood ◽  
E. W. Kairiss ◽  
T. H. Brown
Keyword(s):  
Pyramidal Neurons ◽  
Mossy Fiber ◽  
Classical Method ◽  
Brain Slices ◽  
Long Term Potentiation ◽  
Quantal Size ◽  
Term Potentiation ◽  
Before And After ◽  
Whole Cell Recordings

1. The quantal mechanism underlying the expression of long-term potentiation (LTP) was studied in the mossy-fiber (mf) synapses of the rat hippocampus. Whole-cell recordings were used to measure the excitatory postsynaptic currents (EPSCs) before and after LTP induction in brain slices maintained at 31 +/- 1 degrees C. 2. Evoked EPSCs were recorded from 473 CA3 pyramidal neurons. The mf synapses were stimulated using paired pulses (40-ms interpulse interval) repeated every 2–10 s. At least 400 pairs of mf responses were obtained before and during the expression of LTP, which was produced by high-frequency (100 Hz) mf stimulation. Sufficiently stationary data were obtained from five neurons that exhibited LTP and that also satisfied strict criteria and procedures that are necessary for eliciting and identifying unitary mf responses. 3. Three independent lines of evidence implicated a presynaptic component to the mechanism underlying mf LTP. The first was based on a graphical version of the classical method of variance. The graphical variance (GV) method was evaluated by clamping the cell at two different holding potentials during paired-pulse facilitation (PPF). The results indicated that the GV method can distinguish changes in mean quantal content m and mean quantal size q in rat mf synapses. The same analysis, when applied to PPF before and after LTP induction, indicated that both result from an increase in m. 4. The second line of evidence was based on the classical method of failures. Consistent with the inference that mf LTP is due to an increase in m, there was a statistically significant reduction in the number of quantal release failures.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal infection and fever during late gestation are associated with altered synaptic transmission in the hippocampus of juvenile offspring rats

2008 ◽  
Vol 295 (5) ◽  
pp. R1563-R1571 ◽  
Author(s):  
Germaine C. Lowe ◽  
Giamal N. Luheshi ◽  
Sylvain Williams
Keyword(s):  
Synaptic Transmission ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Late Gestation ◽  
Maternal Infection ◽  
Term Potentiation ◽  
Increased Risk ◽  
Near Term

Prenatal exposure to infection is known to affect brain development and has been linked to increased risk for schizophrenia. The goal of this study was to investigate whether maternal infection and associated fever near term disrupts synaptic transmission in the hippocampus of the offspring. We used LPS to mimic bacterial infection and trigger the maternal inflammatory response in near-term rats. LPS was administered to rats on embryonic days 15 and 16 and hippocampal synaptic transmission was evaluated in the offspring on postnatal days 20–25. Only offspring from rats that showed a fever in response to LPS were tested. Schaffer collateral-evoked field excitatory postsynaptic potentials (fEPSPs) and fiber volleys in CA1 of hippocampal slices appeared smaller in offspring from the LPS group compared with controls, but, when the fEPSPs were normalized to the amplitude of fiber volleys, they were larger in the LPS group. In addition, intrinsic excitability of CA1 pyramidal neurons was heightened, as antidromic field responses in the LPS group were greater than those from control. Short-, but not long-term plasticity was impaired since paired-pulse facilitation of the fEPSP was attenuated in the LPS group, whereas no differences in long-term potentiation were noted. These results suggest that LPS-induced inflammation during pregnancy produces in the offspring a reduction in presynaptic input to CA1 with compensatory enhancements in postsynaptic glutamatergic response and pyramidal cell excitability. Neurodevelopmental disruption triggered by prenatal infection can have profound effects on hippocampal synaptic transmission, likely contributing to the memory and cognitive deficits observed in schizophrenia.

Distinct synaptic loci of Ca2+/calmodulin-dependent protein kinase II necessary for long-term potentiation and depression

1996 ◽  
Vol 76 (3) ◽  
pp. 2097-2101 ◽  
Author(s):  
P. K. Stanton ◽  
A. T. Gage
Keyword(s):  
Pyramidal Neurons ◽  
De Novo ◽  
Hippocampal Slices ◽  
Low Frequency ◽  
Long Term Potentiation ◽  
Term Potentiation ◽  
Bath Application ◽  
Dependent Protein

1. Extracellular bath application of the selective Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor KN-62 to hippocampal slices in vitro blocked the induction of long-term depression (LTD) by low-frequency Schaffer collateral stimulation (1 Hz/15 min) of the same concentration as has been shown previously to prevent induction of long-term potentiation (LTP) at these synapses. 2. In contrast, postsynaptic intracellular infusion of KN-62 into single CA1 pyramidal neurons did not prevent induction of LTD, although it was quite effective in blocking LTP. 3. We conclude that there is a presynaptic CaMKII that must be activated to induce LTD, whereas postsynaptic CaMKII stimulation is needed to evoke LTP. 4. Bath application of KN-62 also blocked depotentiation by low-frequency stimuli of previously induced LTP, suggesting that induction of depotentiation and de novo LTD may require the same CaMKII-dependent mechanisms.

scholarly journals Preconditioning In Vivo Ischemia Inhibits Anoxic Long-Term Potentiation and Functionally Protects CA1 Neurons in the Gerbil

1998 ◽  
Vol 18 (3) ◽  
pp. 288-296 ◽  
Author(s):  
Kensuke Kawai ◽  
Tadayoshi Nakagomi ◽  
Takaaki Kirino ◽  
Akira Tamura ◽  
Nobufumi Kawai
Keyword(s):  
Nmda Receptor ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Forebrain Ischemia ◽  
Term Potentiation ◽  
Induced Tolerance

Preconditioning with sublethal ischemia induces tolerance to subsequent lethal ischemia in neurons. We investigated electrophysiologic aspects of the ischemic tolerance phenomenon in the gerbil hippocampus. Gerbils were subjected to 2 minutes of forebrain ischemia (preconditioning ischemia). Some of them were subjected to a subsequent 5 minutes of forebrain ischemia 2 to 3 days after the preconditioning ischemia (double ischemia). Hippocampal slices were prepared from these gerbils subjected to the preconditioning or double ischemia, and field excitatory postsynaptic potentials were recorded from CA1 pyramidal neurons. Capacity for long-term potentiation triggered by tetanic stimulation (tetanic LTP) was transiently inhibited 1 to 2 days after the double ischemia but then recovered. Latency of anoxic depolarization was not significantly different between slices from preconditioned gerbils and those from sham-operated gerbils when these slices were subjected to in vitro anoxia. Postanoxic potentiation of N-methyl-D-aspartate (NMDA) receptor-mediated transmission (anoxic LTP) was inhibited in slices from gerbils 2 to 3 days after the preconditioning ischemia, whereas it was observed in slices from sham-operated gerbils and gerbils 9 days after the preconditioning ischemia. These results suggest that protection by induced tolerance is (1) not only morphologic but also functional, and (2) expressed in inhibiting postischemic overactivation of NMDA receptor-mediated synaptic responses.

Glutamate-induced long-term potentiation enhances spontaneous EPSC amplitude but not frequency

1996 ◽  
Vol 75 (5) ◽  
pp. 1909-1918 ◽  
Author(s):  
R. J. Cormier ◽  
P. T. Kelly
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
Ca1 Pyramidal Neurons ◽  
New Information ◽  
Term Potentiation ◽  
The Central Nervous System ◽  
Spontaneous Action ◽  
Repetitive Electrical Stimulation

1. Many examples of long-term potentiation (LPT) are induced by repetitive electrical stimulation of presynaptic axons. LTP also is induced by direct glutamate iontophoresis (1 M, 1-2 microA, 10 s) onto postsynaptic neurons in hippocampal slices without evoked presynaptic stimulation; this form of LTP is called "ionto-LTP". The studies herein test the hypothesis that ionto-LTP is expressed primarily through postsynaptic mechanisms. 2. Whole cell recordings were used to examine the amplitude and frequency of spontaneous excitatory postsynaptic currents (sEPSCs) in CA1 pyramidal neurons. sEPSCs were composed of an equal mixture of tetrodotoxin (TTX)-insensitive miniature EPSCs and EPSCs that appeared to result from spontaneous action potentials (i.e., TTX-sensitive EPSCs). The detection of all sEPSCs was virtually eliminated by 6-cyano-7-nitroquinoxaline-2,3-dione (20 microM), suggesting that sEPSCs were glutamate-mediated synaptic events. 3. Changes in the amplitude and frequency of sEPSCs were examined during the expression of ionto-LTP to obtain new information about the cellular location of mechanisms involved in synaptic plasticity. Our findings show that ionto-LTP expression results in increased sEPSC amplitude in the absence of lasting increases in sEPSC frequency. 4. Potentiation of sEPSC amplitude without changes in sEPSC frequency has been previously interpreted to be due to postsynaptic mechanisms. Although this interpretation is supported by findings from peripheral synapses, its application to the central nervous system is unclear. We have considered alternative mechanisms. Models based on increased release probability for action potential dependent transmitter release appeared insufficient to explain our results. The most straightforward interpretation of our results is that LTP induced by glutamate iontophoresis on dendrites of CA1 pyramidal neurons is mediated largely by postsynaptic changes.

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