Simultaneous recording of local electrical activity, partial oxygen tension and temperature in the rat hippocampus with a chamber-type microelectrode. Effects of anaesthesia, ischemia and epilepsy

T. Freund, G. Buzsáki, O. J. Prohaska, A. Leon, P. Somogyi

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

A miniature multiple thin-film recording sensor was used to measure simultaneously the electrical activity, oxygen content and temperature of brain tissue. The chamber-type potential sensor was an Ag/AgCl electrode covered by an Si3N4 (silicon nitride) chamber. The chamber-type oxygen sensor consisted of an Au-Ag/AgCl two-electrode electrochemical cell embedded in an electrolyte-filled Si3N4 chamber. The temperature sensor was a thin-film germanium resistor. The different sensors were spaced 300 μm apart. Anaesthetics (pentobarbital, chloral hydrate, chlornembutal, halothane) were shown to depress electrical activity and to increase local oxygen tension in the hippocampus. Halothane, but not the other anaesthetics, also increased the current output of the oxygen sensor when tested in saline bath, indicating that the apparent increase in measured oxygen levels during halothane anaesthesia was partly due to an electrochemical effect of halothane on the oxygen sensors. The decrease of tissue oxygen consumption produced by the other anaesthetics is likely to be the result of metabolic depression. Cerebral ischemia, evoked by cauterization of the vertebral arteries and occlusion of the carotid arteries for 30 min, resulted in the disappearance of both spontaneous and evoked electrical activity in the hippocampus and a decrease of both local temperature and oxygen tension. There was a marked overshoot of the oxygen tension to above preocclusion level following the release of the carotid arteries. As soon as electrical activity returned, the oxygen tension fell again, often below the lowest level seen during the ischemie period. This secondary decrease of oxygen level could be reversed by administration of supplementary small doses of anaesthetic. The anaesthetic-induced increase in oxygen tension was accompanied by a marked decrease in electroencephalogram amplitude and frequency. During electrically induced seizures a decrease in hippocampal oxygen content occurred and was accompanied by an increase of local temperature. Since the rectal temperature was kept constant, the changes in temperature are likely to reflect changes in blood perfusion of the recorded area. These findings are in agreement with previous observations made with conventional electrodes. In addition, the miniature size of the chamber-type microelectrode assembly allows a correlated monitoring of parallel physiological changes with high spatial and temporal resolution during anaesthesia, ischemia and epilepsy.

Original languageEnglish
Pages (from-to)539-549
Number of pages11
JournalNeuroscience
Volume28
Issue number3
DOIs
Publication statusPublished - 1989

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Microelectrodes
Epilepsy
Hippocampus
Ischemia
Anesthesia
Oxygen
Temperature
Anesthetics
Halothane
Electrodes
Carotid Arteries
Chloral Hydrate
Germanium
Cautery
Vertebral Artery
Physiologic Monitoring
Pentobarbital
Motion Pictures
Brain Ischemia
Baths

ASJC Scopus subject areas

  • Neuroscience(all)

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Simultaneous recording of local electrical activity, partial oxygen tension and temperature in the rat hippocampus with a chamber-type microelectrode. Effects of anaesthesia, ischemia and epilepsy. / Freund, T.; Buzsáki, G.; Prohaska, O. J.; Leon, A.; Somogyi, P.

In: Neuroscience, Vol. 28, No. 3, 1989, p. 539-549.

Research output: Contribution to journalArticle

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