Inhibitory effect of propofol on ketamine-induced c-Fos expression in the rat posterior cingulate and retrosplenial cortices is mediated by GABAA receptor activation.
BACKGROUND
Non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists, including ketamine, have psychotomimetic activities and cause neuronal damage in the posterior cingulate and retrosplenial cortices (PC/RS), which are suggested to be the brain regions responsible for their psychotomimetic activities. We previously demonstrated that ketamine induced marked c-Fos (c-fos protein) expression in the rat PC/RS, which was inhibited by propofol, and the expression was closely related to ketamine-induced abnormal behavior. In the present study, we investigated whether the inhibition by propofol was mediated by GABAA receptor receptor activation.


METHODS
Using Wistar rats, propofol alone, propofol with bicuculline or propofol with flumazenil was injected intravenously and then continuously infused. Fifteen minutes later, 100 mg kg-1 of ketamine or normal saline was injected intraperitoneally. Two hours after the ketamine or saline injection, the brain was extracted and brain sections were prepared, and c-Fos expression was detected using immunohistochemical methods.


RESULTS
Ketamine induced marked c-Fos expression in the PC/RS (171 +/- 9/0.4 mm2), which was significantly inhibited by propofol (5 +/- 5/0.4 mm2). The inhibition by propofol was disinhibited dose-dependently by both bicuculline (0.5 and 1.0 mg kg-1 bicuculline groups: 46 +/- 15 and 143 +/- 16, respectively) and flumazenil (0.1 and 1.0 mg kg-1 flumazenil groups: 79 +/- 6 and 130 +/- 15, respectively).


CONCLUSIONS
These results demonstrate that the inhibitory effect of propofol on ketamine-induced c-Fos expression in the PC/RS is mediated by GABAA receptor activation, and suggests that ketamine-induced psychoneuronal adverse effects may be suppressed by propofol via the activation of GABAA receptors.
Nakao
S
S
Department of Anesthesiology, Kansai Medical University, Moriguchi, Osaka, Japan. nakaos@takii.kmu.ac.jp
Nagata
A
A
Miyamoto
E
E
Masuzawa
M
M
Murayama
T
T
Shingu
K
K
D000778:Anesthetics, Dissociative / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D004569:Electroencephalography / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005442:Flumazenil / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D018757:GABA Modulators / Q000494:pharmacology; D058785:GABA-A Receptor Agonists; D005786:Gene Expression Regulation / Q000187:drug effects*; D016762:Genes, fos; D006179:Gyrus Cinguli / Q000187:drug effects / Q000378:metabolism*; D006439:Hemodynamics / Q000187:drug effects; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D015742:Propofol / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D000778:Anesthetics, Dissociative; D018686:Anesthetics, Intravenous; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018757:GABA Modulators; D058785:GABA-A Receptor Agonists; D005442:Flumazenil; D007649:Ketamine; D001640:Bicuculline; D015742:Propofol