Morphological alterations in the hippocampus following hypobaric hypoxia

Abstract

<jats:p> 1 The morphological consequences of hypobaric hypox ia, exposure to reduced pressure atmospheres, were examined in the hippocampus of male Fischer 344 rats. Severe chronic hypoxia can produce permanent neuronal damage with hippocampal structures being especially vulnerable. </jats:p><jats:p> 2 Hippocampal morphology was studied using histolo gical observations after a 4 day exposure to sea level, 5500 m, or 6400 m. Two groups tested at 6400 m were sacrificed at different intervals following exposure, 72 and 144 h, to examine the effect of post-exposure time on neuronal damage. </jats:p><jats:p> 3 Histological damage was observed in rats' brains following exposure to altitude, with cell degeneration and death increasing as altitude increased. In addition, it was found that the longer the time following exposure before sacrifice, the more noticeable the damage, suggest ing delayed neurotoxicity. Increases in the number of damaged cells following altitude were significant for the CA3 region of one 6400 m group; however, other differ ences did not reach statistical significance. Rats exposed to altitude for 4 days ate less and lost significantly more weight than did animals at sea level. </jats:p><jats:p> 4 It appears that 4 days of exposure to altitudes less than or equal to 6400 m does produce changes in the CA3 subfield, but the damage is different than that seen with other models of non-transient ischemia. </jats:p>

Neuropsychological Functioning Associated with High-Altitude Exposure

“…This causes cellular death after the postsynaptic neuron has released its reserves of glutamate producing a toxic flow that extends to adjacent neurons (Schousboe et al, 1997;Pinel, 2001). The considerable presence of glutamatergic cells in the hippocampus explains partially the enhanced sensitivity of this structure to conditions of hypobaric hypoxia (Gozal et al, 2001;Shukitt-Hale et al, 1996). These findings have not been confirmed in human investigations analyzing through imaging techniques the damage to the encephalon after climbs to peaks above 8,000 m without supplementary oxygen (Garrido et al, 1995;Hacket et al, 1998).…”

“…The physiological measurement was more sensitive than the behavioral assessment, in this case the Morris Water Maze (MWM). This test did not indicate significant damages up to 5,950 m. This author noticed damages in area CA3 in the hippocampus after exposing animals to an altitude of 6,400 m for 4 days (Shukitt-Hale et al, 1996). Gozal et al (2001) used immunohistochemistry to record an increase in apoptosis in area CA1 of the hippocampus after 2 days of exposure to intermittent hypoxia (10/21% O 2 ).…”

Cognitive performance, mood, and neurological status at high terrestrial elevation

“…79 ' 80 Interestingly, VOT separation width (in milliseconds) and the latency to process sentences were correlated -0. 77. 7980 This correlation coefficient implies that 60% of the impaired processing of sentences under these conditions was predicted by the VOT index.…”

“…106 In yet another study with rats, morphological changes were observed with light microscopy in rats' brains following a 4-day exposure to altitude. 77 Damage was observed in some rats exposed to altitudes of 5,500 or 6,400 m, with cell degeneration and death increasing as altitude increased. Also, the longer the time following exposure before sacrifice, the more noticeable the damage, which suggests delayed neurotoxicity.…”

Involvement of the different extracts from roots of Salvia miltiorrhiza Bunge on acute hypobaric hypoxia-induced cardiovascular effects in rats – preliminary report

“…On the other hand, under certain conditions, a short episode of hypoxia exerts beneficial action on the central nervous system, as shown by the protective role of hypoxia preconditioning (Gidday et al 1994, Cantagrel et al 2003. Due to the fact that the rat brain might be less sensitive to hypoxia than the human brain (Shukitt-Hale et al 1996) and a duration of hypoxia condition in the experiment was relatively short, therefore the negative effect of hypobaric hypoxia on motor coordination of rats can be excluded. Moreover, the administration of both extracts has led to normalization to control values of this parameter.…”