Journal ArticleDOI
High pressure modulation of NMDA receptor dependent excitability
Amir Mor,Yoram Grossman +1 more
Reads0
Chats0
TLDR
It is postulated that significant hyperexcitability is attained at pressure only when the normal fast fEPSP is intact and that the decrease in late fE PSs was associated with a reduction of the total number of PSs in the train, apparently without a change in the synaptic efficacy.Abstract:
Pressure above 1.1 MPa induces in mammals and humans the high pressure neurological syndrome (HPNS). HPNS is characterized by cognitive and motor decrements associated with sleep disorders, EEG changes, tremor, and convulsions that ultimately may lead to death. Previous theories proposed that augmented response of the glutamatergic N-methyl-D-aspartate receptor (NMDAR) or reduced GABAergic inhibition may be involved. Recently, we have reported that isolated NMDAR response was augmented at high pressure. We now test whether this augmentation induces neuronal hyperexcitability. We studied high pressure effects on pharmacologically isolated NMDAR field excitatory postsynaptic potentials (fEPSPs) and on their efficacy in generating population spikes (PSs). Sprague-Dawley male rats were used. Hippocampal coronal brain slices were prepared, constantly superfused with physiological solutions, gas-saturated at normobaric pressure, and compressed up to 10.1 MPa with helium. fEPSPs and PSs were recorded from the dendritic and the somatic layers of CA1 pyramidal neurons in response to Schaefer collaterals stimulation with trains of five stimuli at 25 Hz. Pressure caused PSs to appear earlier in the train. However, PS delay, rise time and decay time were increased and PS amplitude, frequency, and number were decreased in the last responses in the train. The decrease in late fEPSPs was associated with a reduction of the total number of PSs in the train, apparently without a change in the synaptic efficacy. These results may partially explain the neuronal hyperexcitability observed at pressure. Therefore, it is postulated that significant hyperexcitability is attained at pressure only when the normal fast fEPSP is intact.read more
Citations
More filters
Journal ArticleDOI
Hyperbaric hyperoxia and normobaric reoxygenation increase excitability and activate oxygen-induced potentiation in CA1 hippocampal neurons
TL;DR: It is postulate that transient acute hyperoxia stimulus, whether caused by breathing HBO or reoxygenation following hypoxia (e.g., disordered breathing), is a powerful stimulant for orthodromic activity and neural plasticity in the CA1 hippocampus.
Journal ArticleDOI
Major dorsoventral differences in the modulation of the local CA1 hippocampal network by NMDA, mGlu5, adenosine A2A and cannabinoid CB1 receptors.
TL;DR: It is proposed that the higher modulatory role of A2AR and mGluR5, in combination with the role of CB1Rs, provide DH with higher functional flexibility of its NMDARs, compared with VH.
Journal ArticleDOI
The efficacy of physiological and pharmacological N-methyl-d-aspartate receptor block is greatly reduced under hyperbaric conditions
A. Mor,Y. Grossman +1 more
TL;DR: It is concluded that hyperbaric pressure reduces the efficacy of these NMDAR blockers that may be associated with the receptor conformational change(s) and provides additional mechanism for pressure over activation of N MDAR.
Journal ArticleDOI
The role of ontogeny in physiological tolerance: decreasing hydrostatic pressure tolerance with development in the northern stone crab Lithodes maja.
TL;DR: A decrease in the acute high-pressure tolerance limit as ontogeny advances is suggested, as reflected by a shift in the hydrostatic pressure at which significant differences are observed.
Journal ArticleDOI
Pressure-selective modulation of NMDA receptor subtypes may reflect 3D structural differences
TL;DR: It is concluded that the NMDAR's diverse responses to HP may lead to selective HP effects on different brain regions, and the need for a re-evaluation of deep-diving safety guidelines is suggested.
References
More filters
Journal ArticleDOI
Effects of hydrostatic pressure on membrane processes. Sodium channels, calcium channels, and exocytosis.
TL;DR: The process of exocytosis is the most likely site at which hydrostatic pressure can act to produce nervous disorders, and pressure can be a useful tool in the investigation of other cellular responses, since it was able to separate different steps occurring during exocyTosis owing to their different activation volumes.
Journal ArticleDOI
Pressure dependence of the potassium currents of squid giant axon
TL;DR: The effects of hydrostatic pressures up to 62 MPa upon the voltage-clamp currents of intact squid giant axons were measured using mineral oil as the pressure transmitting medium and the kinetics of Na inactivation produced by conditioning prepulses of −50 or −60 mV was little affected over the whole range of pressures explored.
Journal ArticleDOI
Pressure and temperature: time-dependent modulation of membrane properties in a bifurcating axon.
Yoram Grossman,Joan J. Kendig +1 more
TL;DR: A crustacean bifurcating motor neuron that selectively controls output to its daughter branches was exposed to helium pressure of 1-200 atmospheres and temperatures of 9-22 degrees C, resulting in a result consistent with pressure inhibition of the electrogenic sodium pump in this axon.
Journal Article
High pressure nervous syndrome
Journal ArticleDOI
Evoked potential changes in rat hippocampal slices under helium pressure.
L. Fagni,F. Zinebi,Maurice Hugon +2 more
TL;DR: The present results support the hypothesis of a helium pressure-induced depolarization of hippocampal neurons, and other possible mechanisms are discussed.