Antagonistic effect of physostigmine on ketamine-induced anesthesia.
Effects of physostigmine on ketamine-induced anesthesia and analgesia were studied in male Sprague-Dawley rats using behavioral tests. Rats were divided into six groups. Immediately after loss of the righting reflex following an intraperitoneal injection of ketamine 75 mg/kg, each group of rats was given an intraperitoneal injection of either physostigmine 0.05, 0.1, 0.2, 0.4, 0.6 mg/kg or saline as the control, respectively. Physostigmine 0.1 mg/kg caused the greatest antagonistic effect on ketamine anesthesia as indicated by sleeping time, duration of ataxia and motor coordination. The antagonistic effects of physostigmine were reduced by a dose of physostigmine of greater than 0.1 mg/kg. However, at no dose did physostigmine antagonize ketamine analgesia as indicated by the tail-flick latency. Physostigmine (0.4 and 0.6 mg/kg) itself had analgesic and motor-suppressive actions. It can therefore be presumed that there is a limited threshold of the dose of physostigmine which develops an antagonistic effect on ketamine anesthesia due to the motor-suppressive action. It is also confirmed that physostigmine itself produces analgesia, and does not antagonize ketamine-induced analgesia.
Mimura
M
M
Department of Anesthesiology, Sapporo Medical College, Japan.
Namiki
A
A
Kishi
R
R
Ikeda
T
T
Miyake
H
H
D000758:Anesthesia; D000818:Animals; D001259:Ataxia / Q000139:chemically induced / Q000523:psychology; D004305:Dose-Response Relationship, Drug; D007649:Ketamine / Q000037:antagonists & inhibitors*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010830:Physostigmine / Q000494:pharmacology*; D004856:Postural Balance / Q000187:drug effects; D011597:Psychomotor Performance; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D012890:Sleep / Q000187:drug effects; D013997:Time Factors
D007649:Ketamine; D010830:Physostigmine