Indirect activation of adenosine A1 receptors in cultured rat hippocampal neurons by volatile anaesthetics.
OBJECTIVE
Volatile anaesthetics depress excitatory signal transmission by potentiating the inhibitory action of GABAA receptors and there is strong evidence that this is related with anaesthesia. Using primary hippocampal cultures we analyzed the possibility that the volatile anaesthetics enflurane and sevoflurane depress excitatory signal transmission by activation of adenosine A1 receptors.


METHODS
Primary rat hippocampal cultures on 4 cm poly-L-lysine coated glass coverslips were loaded with the Ca2+-indicator fluo-3 and incorporated in a gastight, temperature-controlled perfusion chamber. The intracellular Ca2+-concentration was monitored with a confocal laser-scanning microscope (BioRad) using the 488 nm laser line of a krypton-argon laser for excitation and the Lasersharp Acquisition software for analysis.


RESULTS
Continuous perfusion in Mg2+-free medium generated spontaneous synchronized calcium oscillations, which were dose dependently depressed by the volatile anaesthetics enflurane and sevoflurane (0.25-1 minimum alveolar concentration). Addition of 100 nmol of 2-chloro-N6-cyclopentyladenosine, a specific adenosine A1 receptor antagonist, partly reversed the anaesthetic-induced inhibition of the oscillation amplitude of the oscillating cells. The effect of the anaesthetics was mimicked by the addition of S-(p-nitrobenzyl)-6-thioguanosine, an adenosine transport inhibitor and by the addition of 5-amino-5-deoxyadenosine, an inhibitor of adenosine kinase.


CONCLUSIONS
The volatile anaesthetics sevoflurane and enflurane activate adenosine A1 receptors in primary rat hippocampal cultures. This effect is mediated by liberation of adenosine most likely by an interaction of the volatile anaesthetics with adenosine transport or key enzymes in adenosine metabolism.
Tas
P W L
PW
University of Würzburg, Center of Operative Medicine, Department of Anaesthesiology, Würzburg, Germany. tas_p@klinik.uni-wuerzburg.de
Eisemann
C
C
Roewer
N
N
D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D058916:Adenosine A1 Receptor Antagonists; D000248:Adenosine Kinase / Q000037:antagonists & inhibitors; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D003839:Deoxyadenosines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004737:Enflurane / Q000494:pharmacology; D006151:Guanosine / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects*; D008274:Magnesium / Q000494:pharmacology; D008738:Methyl Ethers / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D043682:Receptor, Adenosine A1 / Q000187:drug effects*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D000077149:Sevoflurane; D015398:Signal Transduction / Q000187:drug effects; D013872:Thionucleosides / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
D058916:Adenosine A1 Receptor Antagonists; D018685:Anesthetics, Inhalation; D003839:Deoxyadenosines; D008738:Methyl Ethers; D058915:Purinergic P1 Receptor Antagonists; D043682:Receptor, Adenosine A1; D016194:Receptors, N-Methyl-D-Aspartate; D013872:Thionucleosides; D014970:Xanthines; D006151:Guanosine; C002121:6-(4-nitrobenzylthio)guanosine; C057928:5'-amino-5'-deoxyadenosine; C058394:2-chloro-N(6)cyclopentyladenosine; D000077149:Sevoflurane; D004737:Enflurane; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000248:Adenosine Kinase; D008274:Magnesium; D000241:Adenosine