Center for Integrative Brain Research

Seattle, WA, United States

Center for Integrative Brain Research

Seattle, WA, United States

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Garcia III A.J.,Center for Integrative Brain Research | Putnam R.W.,Wright State University | Dean J.B.,Hyperbaric Biomedical Research Laboratory
Journal of Applied Physiology | Year: 2010

Breathing hyperbaric oxygen (HBO) is common practice in hyperbaric and diving medicine. The benefits of breathing HBO, however, are limited by the risk of central nervous system O2 toxicity, which presents as seizures. We tested the hypothesis that excitability increases in CA1 neurons of the rat hippocampal slice (400 μm) over a continuum of hyperoxia that spans normobaric and hyperbaric pressures. Amplitude changes of the orthodromic population spike were used to assess neuronal O2 sensitivity before, during, and following exposure to 0, 0.6, 0.95 (control), 2.84, and 4.54 atmospheres absolute (ATA) O2. Polarographic O2 electrodes were used to measure tissue slice PO2 (Pt O2). In 0.95 ATA O2, core PtO 2 at 200 μm deep was 115 ± 16 Torr (mean ± SE). Increasing O2 to 2.84 and 4.54 ATA increased core PtO 2 to 1,222 ± 77 and 2,037 ± 157 Torr, respectively. HBO increased the orthodromic population spike amplitude and usually induced hyperexcitability (i.e., secondary population spikes) and, in addition, a longlasting potentiation of the orthodromic population spike that we have termed "oxygen-induced potentiation" (OxIP). Exposure to 0.60 ATA O 2 and hypoxia (0.00 ATA) decreased core Pto2 to 84 ± 6 and 20 ± 4 Torr, respectively, and abolished the orthodromic response. Reoxygenation from 0.0 or 0.6 ATA O2, however, usually produced a response similar to that of HBO: hyperexcitability and activation of OxIP. We conclude that CA1 neurons exhibit increased excitability and neural plasticity over a broad range of Pto2, which can be activated by a single, hyperoxic stimulus. We 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. Copyright © 2010 the American Physiological Society.


PubMed | Center for Integrative Brain Research
Type: Journal Article | Journal: Journal of applied physiology (Bethesda, Md. : 1985) | Year: 2010

Breathing hyperbaric oxygen (HBO) is common practice in hyperbaric and diving medicine. The benefits of breathing HBO, however, are limited by the risk of central nervous system O2 toxicity, which presents as seizures. We tested the hypothesis that excitability increases in CA1 neurons of the rat hippocampal slice (400 microm) over a continuum of hyperoxia that spans normobaric and hyperbaric pressures. Amplitude changes of the orthodromic population spike were used to assess neuronal O2 sensitivity before, during, and following exposure to 0, 0.6, 0.95 (control), 2.84, and 4.54 atmospheres absolute (ATA) O2. Polarographic O2 electrodes were used to measure tissue slice PO2 (PtO2). In 0.95 ATA O2, core PtO2 at 200 microm deep was 11516 Torr (meanSE). Increasing O2 to 2.84 and 4.54 ATA increased core PtO2 to 1,22277 and 2,037157 Torr, respectively. HBO increased the orthodromic population spike amplitude and usually induced hyperexcitability (i.e., secondary population spikes) and, in addition, a long-lasting potentiation of the orthodromic population spike that we have termed oxygen-induced potentiation (OxIP). Exposure to 0.60 ATA O2 and hypoxia (0.00 ATA) decreased core PtO2 to 846 and 204 Torr, respectively, and abolished the orthodromic response. Reoxygenation from 0.0 or 0.6 ATA O2, however, usually produced a response similar to that of HBO: hyperexcitability and activation of OxIP. We conclude that CA1 neurons exhibit increased excitability and neural plasticity over a broad range of PtO2, which can be activated by a single, hyperoxic stimulus. We 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.

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