NOx- concentrations in the rat hippocampus and striatum have no direct relationship to anaesthesia induced by ketamine |
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Authors: | Wu J Kikuchi T Wang Y Sato K Okumura F |
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Institution: | Department of Anaesthesiology, Yokohama City University School of Medicine, Japan. |
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Abstract: | Using microdialysis, we have examined the effects of ketamine on
concentrations of total nitric oxide oxidation products (NOx-) in the rat
hippocampus and striatum in vivo to investigate the relationship between
anaesthesia and NOx- production in the brain. Ketamine 25, 50 and 100 mg
kg-1 i.p. increased NOx- concentrations to mean 125 (SD 13)%, 165 (11)% and
193 (13)% of basal, respectively, in the hippocampus and to 122 (12)%, 147
(7)% and 177 (14)% of basal in the striatum. Local perfusion with ketamine
50 and 100 mumol litre-1 into the hippocampus or striatum increased NOx-
concentrations to 212 (32)% and 291 (17)% of basal, respectively, in the
hippocampus and to 148 (20)% and 201 (18)% of basal in the striatum.
Ketamine 50 and 100 mg kg- 1 i.p. caused dose-dependent prolongation of
loss of the righting reflex (LRR) and 100 mg kg-1 i.p. also caused loss of
the corneal reflex (LCR). Local perfusion of ketamine did not provoke LRR
or LCR. Inhibition of NOS by L-NAME 100 mg kg-1 i.p. decreased hippocampal
NOx- concentrations to 58 (7)% of basal and did not provoke LRR or LCR.
Although the effect of ketamine-induced increases in hippocampal NOx-
concentrations was significantly depressed by L-NAME, LRR was not affected.
These data imply that NOx- concentrations in the hippocampus or striatum
have no direct relationship to the anaesthetic efficacy of ketamine,
although this requires further investigation.
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