Changes of neuronal activity in areas CA1 and CA3 during anoxia and normoxic or hyperoxic reoxygenation in juvenile rat organotypic hippocampal slice cultures.
In neonates, asphyxia is usually followed by hyperoxic treatment. In order to study whether hyperoxic reoxygenation might cause additional impairment of neuronal function, we subjected organotypic hippocampal slice cultures of juvenile rats (7 DIV, P6-8) to 30 min anoxia followed by 60 min hyperoxic or normoxic reoxygenation (95% or 19% O2, respectively). Spontaneous and evoked field potentials as well as [Ca2+]o were recorded in the pyramidal layer of area CA1 or area CA3. In area CA1, 30 min of anoxia led to decline of evoked field potential amplitudes by on average 67% and to profound changes in field potential characteristics and Ca2+ homeostasis which were not related to outcome after reoxygenation. Hyperoxic reoxygenation resulted first in a fast recovery of the field potential amplitude to 82% of the control value and then, in 75% of slice cultures, in a large negative field potential shift accompanied by a prolonged decrease of [Ca2+]o and loss of excitability outlasting the experiment. Recovery of field potential amplitude under normoxic conditions stayed poor, with a first increase to 51% and a second decrease to 22%. In contrast, field potential amplitude in area CA3 recovered to 80% of the initial amplitude, irrespective of the reoxygenation mode. The selective loss of function during hyperoxic reoxygenation in area CA1 might be a first sign of neuronal injury that we observed 1 h after end of hyperoxic reoxygenation in a previous study. Whether the poor outcome after normoxic reoxygenation would favour long-term recovery remains to be determined.
Hoffmann
Ulrike
U
Institut für Neurophysiologie, Tucholskystr. 2, D 10117 Berlin, Germany.
Pomper
Jörn
J
Graulich
Johannes
J
Zeller
Melanie
M
Schuchmann
Sebastian
S
Gabriel
Siegrun
S
Maier
Rolf F
RF
Heinemann
Uwe
U
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D016009:Chi-Square Distribution; D013181:Cortical Spreading Depression / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D006624:Hippocampus / Q000473:pathology* / Q000503:physiopathology; D006931:Hyperbaric Oxygenation / Q000379:methods; D000860:Hypoxia / Q000503:physiopathology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D009924:Organ Culture Techniques; D010100:Oxygen / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D010100:Oxygen; D002118:Calcium