Conditioning hypoxia in vivo alters neuronal excitability of hippocampal neurones of rats in vitro and in vivo.
OBJECTIVE
Moderate normobaric hypoxia causes long-lasting protection against damage induced by a second ischemic or traumatic insult. The changes induced by such conditioning hypoxia are not yet fully understood. The protective effect has been described in various publications but other effects seem possible.


METHODS
In order to search for effects of conditioning normobaric hypoxia yet unknown, we measured O-Mg++ potentiation and classical long-term potentiation (LTP) in the CA, region of hippocampal slices seven days after the conditioning procedure. Furthermore, tests were also carried out in chronically implanted rats as to whether LTP was changed in the dentate gyrus after conditioning hypoxia.


RESULTS
In slices taken from animals which received conditioning hypoxia, O-Mg++ potentiation and classical LTP of the population spike were significantly enhanced, when compared to population in two control groups. Anoxic LTP, i.e. increase in the population spike of the field potential in the dentate gyrus immediately after finishing the procedure, and a tendency to elevation of LTP seven days after conditioning were also found in chronically implanted animals which were subjected to conditioning hypoxia.


CONCLUSIONS
lt. may be hypothesized that elevated Ca++ transport in the neurons during conditioning hypoxia is responsible for both long- lasting increases in plastic reactions and the protective effect.
Rüthrich
H L
HL
Institute of Pharmacology and Toxicology, Otto-von-Guericke- University, Leipziger Str. 44, 39120 Magdeburg, Germany. Hiede-Linde.Ruethrich@medizin.uni-magdeburg.de
Krug
M
M
D000818:Animals; D018891:Dentate Gyrus / Q000166:cytology / Q000502:physiology*; D002534:Hypoxia, Brain / Q000503:physiopathology*; D019194:Ischemic Preconditioning; D017774:Long-Term Potentiation / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009043:Motor Activity; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009924:Organ Culture Techniques; D019580:Perforant Pathway / Q000166:cytology / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D008274:Magnesium