α5GABAA receptors regulate hippocampal sharp wave–ripple activity in vitro

Papatheodoropoulos, Costas; Koniaris, Efthymios

doi:10.1016/j.neuropharm.2010.11.022

Cited by 29 publications

(28 citation statements)

References 99 publications

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“…It is noted that spontaneous activation of the VH local network occurred even at small reductions in GABA A Rergic inhibition induced by small concentrations of SR 95531. Small reductions of GABAergic inhibition such as those used in the present study favor the activity of sharp wave—ripples [ 51 ] which is the only one physiological endogenous network activity of the hippocampus. Actually, the generation of the ripple oscillation requires an accurate balance between excitation and inhibition in the local circuitry [ 52 ].…”

Section: Discussionmentioning

confidence: 99%

Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors

Papatheodoropoulos

2015

BMC Neurosci

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BackgroundElucidating specializations of the intrinsic neuronal network between the dorsal and the ventral hippocampus is a recently emerging area of research that is expected to help us understand the mechanisms underlying large scale functional diversification along the hippocampus. The aim of this study was to characterize spontaneous network activity between the dorsal and the ventral hippocampus induced under conditions of partial or complete blockade of GABAergic inhibition (i.e. disinhibition).ResultsUsing field recordings from the CA3 and CA1 fields of hippocampal slices from adult rats I found that ventral compared with dorsal hippocampus slices displayed higher propensity for and higher frequency of occurrence of spontaneous field potentials (spfps) at every level of disinhibition. Also NMDA receptor-depended spfps (spfps-nmda) occurred with higher probability more frequently and were larger in the ventral compared with the dorsal hippocampus. Importantly, blockade of GABAB receptors produced a stronger effect in enhancing the probability of generation of spfps and spfps-nmda in the dorsal compared with the ventral hippocampal slices and increased spfps-nmda only in dorsal slices.ConclusionThese results demonstrate a higher intrinsic neuronal excitability of the ventral compared with the dorsal local circuitry with the considerable contribution of NMDA receptors. Furthermore, the GABAB receptors control the total and the NMDA receptor-dependent excitation much less effectively in the ventral part of the hippocampus. It is proposed that NMDA and GABAB receptors significantly contribute to differentiate local network dynamics between the dorsal and the ventral hippocampus with important implications in the information processing performed along the long hippocampal axis.

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Section: Discussionmentioning

confidence: 99%

Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors

Papatheodoropoulos

2015

BMC Neurosci

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“…SPW-like bursts have been also observed in isolated CA3 slices (Behrens et al, 2006; Kubota et al, 2003; Maier et al, 2003; Papatheodoropoulos and Kostopoulos, 2002; Papatheodoropoulos and Koniaris, 2010) and under in vitro conditions, they are super-regular at 2 to 4 Hz (Maier et al, 2003; Kubota et al, 2003; Colgin et al, 2004; 2005; Behrens et al, 2005, 2007; Dzhala and Staley, 2004; Foffani et al, 2007; Colgin et al, 2004, 2005; Pais et al, 2003; Maier et al, 2003; Both et al, 2008; Traub and Bibbig, 2000; Reichinnek et al, 2010; Wu et al, 2005), in contrast to the irregular SPW-R intervals in vivo. The rhythmic recurrence of SPW-Rs in the CA3 network may be explained by an underlying slow relaxation oscillator (Pikovsky et al, 2001; Sirota et al, 2003; Buzsaki, 2006), in which the occurrence of the SPW burst can be advanced by weak inputs in a time- and input magnitude-dependent manner.…”

Section: Role Of Dentate Gyrus and Entorhinal Cortex In Timing Of Spw-rsmentioning

confidence: 91%

Relationships between Hippocampal Sharp Waves, Ripples, and Fast Gamma Oscillation: Influence of Dentate and Entorhinal Cortical Activity

Sullivan

Csicsvari

Mizuseki

et al. 2011

Journal of Neuroscience

260

317

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Summary Hippocampal sharp waves (SPW) and associated fast (‘ripple’) oscillations in the CA1 region are among the most synchronous physiological patterns in the mammalian brain. Using two-dimensional arrays of electrodes for recording local field potentials and unit discharges in freely moving rats, we studied the emergence of ripple oscillations (140–220 Hz) and compared their origin and cellular-synaptic mechanisms with fast gamma oscillations (90–140 Hz). We show that (a) hippocampal SPW-Rs and fast gamma oscillations are quantitatively distinct patterns but involve the same networks and share similar mechanisms, (b) both the frequency and magnitude of fast oscillations is positively correlated with the magnitude of SPWs, (c) during both ripples and fast gamma oscillations the frequency of network oscillation is higher in CA1 than in CA3, (d) SPWs and associated firing of neurons are synchronous in the dorsal hippocampus and dorso-medial entorhinal cortex but ripples are confined to the CA1 pyramidal layer and its downstream targets and (e) the emergence of CA3 population bursts, a prerequisite for SPW-ripples, is biased by activity patterns in the dentate gyrus and entorhinal cortex, with highest probability of ripples associated with an ‘optimum’ level of dentate gamma power. We hypothesize that each hippocampal subnetwork possesses distinct resonant properties, tuned by the magnitude of the excitatory drive.

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“…These effects are believed to be mediated by the activation of α5‐containing GABA A receptors. α5‐GABA A is responsible for the GABAergic tonic inhibition of pyramidal cells in the CA1 (Caraiscos et al ., ) and α5 inverse agonists increase SWR occurrence in vitro (Papatheodoropoulos & Koniaris, ). Furthermore, a number of studies have shown that memory encoding in the hippocampus both in rodents (Collinson et al ., ; Braudeau et al ., ; Rissman & Mobley, ; Redrobe et al ., ) and humans (Atack, ) can be improved by a5 inverse agonists under certain conditions.…”

Section: Diagnostic and Therapeutic Implicationsmentioning

confidence: 98%

Neural oscillations during non‐rapid eye movement sleep as biomarkers of circuit dysfunction in schizophrenia

Gardner

Kersanté

Jones

et al. 2014

Eur J of Neuroscience

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The neurophysiology of non-rapid eye movement sleep is characterized by the occurrence of neural network oscillations with distinct origins and frequencies, which act in concert to support sleep-dependent information processing. Thalamocortical circuits generate slow (0.25-4 Hz) oscillations reflecting synchronized temporal windows of cortical activity, whereas concurrent waxing and waning spindle oscillations (8-15 Hz) act to facilitate cortical plasticity. Meanwhile, fast (140-200 Hz) and brief (< 200 ms) hippocampal ripple oscillations are associated with the reactivation of neural assemblies recruited during prior wakefulness. The extent of the forebrain areas engaged by these oscillations, and the variety of cellular and synaptic mechanisms involved, make them sensitive assays of distributed network function. Each of these three oscillations makes crucial contributions to the offline memory consolidation processes supported by non-rapid eye movement sleep. Slow, spindle and ripple oscillations are therefore potential surrogates of cognitive function and may be used as diagnostic measures in a range of brain diseases. We review the evidence for disrupted slow, spindle and ripple oscillations in schizophrenia, linking pathophysiological mechanisms to the functional impact of these neurophysiological changes and drawing links with the cognitive symptoms that accompany this condition. Finally, we discuss potential therapies that may normalize the coordinated activity of these three oscillations in order to restore healthy cognitive function.

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α5GABAA receptors regulate hippocampal sharp wave–ripple activity in vitro

Cited by 29 publications

References 99 publications

Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors

Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors

Relationships between Hippocampal Sharp Waves, Ripples, and Fast Gamma Oscillation: Influence of Dentate and Entorhinal Cortical Activity

Neural oscillations during non‐rapid eye movement sleep as biomarkers of circuit dysfunction in schizophrenia

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