Glutamate transporter type 3 knockout mice have a decreased isoflurane requirement to induce loss of righting reflex

Abstract Background: Ketamine is a commonly used anesthetic, but the mechanistic basis for its clinically relevant actions remains to be determined. The authors previously showed that HCN1 channels are inhibited by ketamine and demonstrated that global HCN1 knockout mice are twofold less sensitive to hypnotic actions of ketamine. Although that work identified HCN1 channels as a viable molecular target for ketamine, it did not determine the relevant neural substrate. Methods: To localize the brain region responsible for HCN1-mediated hypnotic actions of ketamine, the authors used a conditional knockout strategy to delete HCN1 channels selectively in excitatory cells of the mouse forebrain. A combination of molecular, immunohistochemical, and cellular electrophysiologic approaches was used to verify conditional HCN1 deletion; a loss-of-righting reflex assay served to ascertain effects of forebrain HCN1 channel ablation on hypnotic actions of ketamine. Results: In conditional knockout mice, HCN1 channels were selectively deleted in cortex and hippocampus, with expression retained in cerebellum. In cortical pyramidal neurons from forebrain-selective HCN1 knockout mice, effects of ketamine on HCN1-dependent membrane properties were absent; notably, ketamine was unable to evoke membrane hyperpolarization or enhance synaptic inputs. Finally, the EC50 for ketamine-induced loss-of-righting reflex was shifted to significantly higher concentrations (by approximately 31%). Conclusions: These data indicate that forebrain principal cells represent a relevant neural substrate for HCN1-mediated hypnotic actions of ketamine. The authors suggest that ketamine inhibition of HCN1 shifts cortical neuron electroresponsive properties to contribute to ketamine-induced hypnosis.

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Application of serial sampling of cerebrospinal fluid in pharmacodynamic studies with a drug active in the CNS: Heptabarbital concentrations at onset and offset of loss of righting reflex in rats

Neuropharmacology ◽

10.1016/0028-3908(88)90128-1 ◽

1988 ◽

Vol 27 (5) ◽

pp. 467-474 ◽

Cited By ~ 7

Author(s):

J. Dingemanse ◽

P.H. Hutson ◽

M.W.E. Langemeijer ◽

G. Curzon ◽

M. Danhof

Keyword(s):

Cerebrospinal Fluid ◽

Loss Of Righting Reflex ◽

Serial Sampling ◽

Righting Reflex

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Investigation of Potassium Chloride for Euthanasia of Anesthetized Marine Toads (Rhinella marina)

Journal of Herpetological Medicine and Surgery ◽

10.5818/jhms-d-21-00009 ◽

2021 ◽

Author(s):

Meghan M. Louis ◽

Gregory Scott ◽

Dustin Smith ◽

Brigid V. Troan ◽

Larry J. Minter ◽

...

Keyword(s):

Potassium Chloride ◽

Potassium Concentration ◽

Plasma Potassium ◽

Post Treatment ◽

Spontaneous Movement ◽

Limits Of Detection ◽

Rhinella Marina ◽

Loss Of Righting Reflex ◽

Righting Reflex ◽

Technique Failure

Euthanasia techniques in amphibians are poorly described and sparsely validated. This study investigated potassium chloride (KCl) for euthanasia of anesthetized marine toads ( Rhinella marina ). Twenty three toads were immersed in buffered MS-222 (2 g/L) for five minutes (min) beyond loss of righting reflex, manually removed, and randomly administered KCl (n = 6/group) via one of three routes: intracardiac at 10 mEq/kg (IC), intracoelomic at 100 mEq/kg (ICe), or immersion at 4500 mEq/L (IMS) or no treatment (C) (n = 5/group). Doppler sounds were assessed continuously from prior to treatment until two min post-treatment and every five min thereafter until sound cessation or resumption of spontaneous movement. Plasma potassium concentration (K+) was measured at the time of Doppler sound cessation in ICe and IMS. In IC, ICe, IMS, and C, Doppler sound cessation occurred in 4/6, 6/6, 6/6, and 1/5 toads with median (range) or mean + SD times of 0.23 (0-4.65), 17.5 + 9.0, 40.6 + 10.9, and >420 min, respectively. Nonsuccess in 2/6 toads in IC was suspected due to technique failure. Plasma K+ exceeded the limits of detection (>9 mmol/L) in 12/12 toads in ICe and IMS. Five of six toads in C resumed spontaneous movement at median (range) times of 327 (300-367) min. KCl delivered via an intracardiac, intracoelomic, or immersion routes resulted in Doppler sound cessation in 16 of 18 toads and may be appropriate for euthanasia of anesthetized marine toads.

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Stereoselective Loss of Righting Reflex in Rats by Isoflurane

Anesthesiology ◽

10.1097/00000542-200009000-00035 ◽

2000 ◽

Vol 93 (3) ◽

pp. 837-843 ◽

Cited By ~ 37

Author(s):

Robert Dickinson ◽

Ian White ◽

William R. Lieb ◽

Nicholas P. Franks

Keyword(s):

Molecular Targets ◽

Maximal Effect ◽

General Anesthetics ◽

General Anesthetic ◽

Response Curves ◽

Loss Of Righting Reflex ◽

Large Numbers ◽

Righting Reflex ◽

Volatile Agents

Background Although it is accepted widely that optically active intravenous general anesthetics produce stereoselective effects in animals, the situation regarding volatile agents is confused. Conventional studies with scarce isoflurane enantiomers have been limited to small numbers of animals and produced conflicting results. By injecting these volatile enantiomers intravenously, however, it is possible to study large numbers of animals and obtain reliable results that can help to identify the molecular targets for isoflurane. Methods Pure isoflurane enantiomers were administered intravenously to rats after solubilization in a lipid emulsion. The ability of each enantiomer to produce a loss of righting reflex was determined as a function of dose, and quantal dose-response curves were constructed. In addition, sleep times were recorded with each enantiomer. Chiral gas chromatography was used to measure relative enantiomer concentrations in the brains of rats injected with racemic isoflurane. Results The S(+)-enantiomer was 40 +/- 8% more potent than the R(-)-enantiomer at producing a loss of righting reflex. The S(+)-enantiomer induced longer sleep times (by about 50%) than did the R(-)-enantiomer. Rats anesthetized by a dose of racemic isoflurane sufficient to achieve a half-maximal effect had essentially identical brain concentrations of the two enantiomers. Conclusions The S(+)-enantiomer of the general anesthetic isoflurane is significantly (P < 0.001) more potent than the R(-)-enantiomer at causing a loss of righting reflex in rats. This confirms the view that isoflurane acts by binding to chiral sites. The observed degree of stereoselectivity provides a useful guide for ascertaining from in vitro experiments which molecular targets are most likely to play major roles in the loss of righting reflex caused by isoflurane.

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Sleep Deprivation Potentiates the Onset and Duration of Loss of Righting Reflex Induced by Propofol and Isoflurane

Anesthesiology ◽

10.1097/00000542-200210000-00024 ◽

2002 ◽

Vol 97 (4) ◽

pp. 906-911 ◽

Cited By ~ 62

Author(s):

Avery Tung ◽

Martin J. Szafran ◽

Bryan Bluhm ◽

Wallace B. Mendelson

Keyword(s):

Sleep Deprivation ◽

Neuronal Networks ◽

Fixed Dose ◽

Patient Response ◽

Disk Rotation ◽

Anesthetic Agents ◽

Loss Of Righting Reflex ◽

Separate Control ◽

Righting Reflex ◽

Time Required

Background Sleep and anesthesia differ physiologically but produce a similar loss of responsiveness to environmental stimuli. Recent data suggest that neuronal networks active in naturally occurring sleep also play a role in the anesthetized state. Changes in the propensity to sleep may then modify the response to anesthetic agents. The authors tested the hypothesis that sleep-deprived rats would require less anesthetic than rested rats to achieve a similar loss of responsiveness. Methods Rats were subjected to a 24-h period of either sleep deprivation or ad libitum activity. Sleep deprivation was produced by placing rats on a disk that rotated when sleep was detected by electroencephalographic and electromyographic (EEG, EMG) monitoring. A fixed dose of anesthetic agent was then administered, and the time required to induce loss of righting reflex was measured. Anesthetic administration was then stopped, and the time to recovery measured. All rats received both treatments separated by 7 days. Results Sleep deprivation reduced the time to loss of righting reflex by 40% for propofol (P < 0.025) and 55% for isoflurane (P < 0.025) and prolonged the time to recovery. In a separate control experiment, exposure to the deprivation environment but with disk rotation modified to allow adequate sleep did not affect the response to anesthetic administration. Conclusions Sleep deprivation significantly potentiated the ability of inhaled and intravenous anesthetic agents to induce a loss of righting reflex. These results support the hypothesis that neuronal networks active in sleep are also involved in the anesthetized state and suggest that sleep deprivation may partly explain the variability in patient response to anesthesia.

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