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At least 19 recordsLinked to original sources

A rapid method for evaluating the behavioral effects of phencyclidine-like dissociative anesthetics in mice.

A simple and rapid method for detecting the behavioral effects of phencyclidine and related dissociative anesthetics is described. Dissociative anesthetics such as phencyclidine (PCP) and dizolcipine, which bind with high affinities at N-methyl-D-aspartate (NMDA) coupled cation channels ("PCP receptors"), produced a dose-related increase in the percentage of mice that fell from a 1.5 cm deep circular arena mounted on a 60 cm platform. A similar behavior was not manifest by other classes of compounds examined including competitive NMDA antagonists, an antagonist at strychnine-insensitive glycine receptors, and sigma-receptor ligands with moderate to low affinities for PCP receptors. Pretreatment of mice with glycine reduced in a dose-dependent manner the percentage of falls elicited by a maximally effective dose of dizolcipine. This simple procedure may prove useful for both the rapid detection of dissociative anesthetics and evaluation of putative PCP antagonists.

Anesthetics↗

Alpha-2 agonist dissociative anesthetic combinations in fallow deer (Cervus dama).

Three anesthetic protocols, each using an alpha-2 agonist sedative in combination with a dissociative anesthetic, were evaluated in 17 captive fallow deer (Cervus dama). The alpha-2 agonist was given first in two of the three protocols: 1) detomidine (0.1-0.2 mg/kg i.m.) followed by tiletamine-zolazepam (3.0-6.3 mg/kg i.m.) and 2) xylazine (0.6-0.9 mg/kg i.m.) followed by tiletamine-zolazepam (4-5 mg/kg i.m.). In the third protocol, xylazine (1.0-6.2 mg/kg i.m.) and ketamine (2.5-5.1 mg/kg i.m.) were given simultaneously. Each of the sedative/anesthetic combinations produced acceptable immobilization in fallow deer and both provide an alternative to narcotic anesthesia.

Adrenergic alpha-Agonists↗

Subunit-dependent inhibition of human neuronal nicotinic acetylcholine receptors and other ligand-gated ion channels by dissociative anesthetics ketamine and dizocilpine.

UNLABELLED: Background The neuronal mechanisms responsible for dissociative anesthesia remain controversial. N-methyl-D-aspartate (NMDA) receptors are inhibited by ketamine and related drugs at concentrations lower than those required for anesthetic effects. Thus, the authors studied whether ligand-gated ion channels other than NMDA receptors might display a sensitivity to ketamine and dizocilpine that is consistent with concentrations required for anesthesia. METHODS: Heteromeric human neuronal nicotinic acetylcholine receptors (hnAChR channels alpha2beta2, alpha2beta4, alpha3beta2, alpha3beta4, alpha4beta2 and alpha4beta4), 5-hydroxytryptamine3 (5-HT3), alpha1beta2gamma2S gamma-aminobutyric acid type A (GABAA) and alpha1 glycine receptors were expressed in Xenopus oocytes, and effects of ketamine and dizocilpine were studied using the two-electrode voltage-clamp technique. RESULTS: Both ketamine and dizocilpine inhibited hnAChRs in a noncompetitive and voltage-dependent manner. Receptors containing beta1 subunits were more sensitive to ketamine and dizocilpine than those containing beta2 subunits. The inhibitor concentration for half-maximal response (IC50) values for ketamine of hnAChRs composed of beta4 subunits were 9.5-29 microM, whereas those of beta2 subunits were 50-92 microM. Conversely, 5-HT3 receptors were inhibited only by concentrations of ketamine and dizocilpine higher than the anesthetic concentrations. This inhibition was mixed (competitive/noncompetitive). GABAA and glycine receptors were very resistant to dissociative anesthetics. CONCLUSIONS: Human nAChRs are inhibited by ketamine and dizocilpine at concentrations possibly achieved in vivo during anesthesia in a subunit-dependent manner, with beta subunits being more critical than alpha subunits. Conversely, 5-HT3, GABAA, and glycine receptors were relatively insensitive to dissociative anesthetics.

Anesthetics, Dissociative↗

Patient acceptance of dissociative anesthetics.

A prospective study was undertaken to evaluate the efficacy, safety, and patient acceptance of low-dose ketamine when used to diminish the pain of local anesthetic injections. The role of diazepam in preventing the untoward psychological effects of ketamine was also investigated. Our findings, derived from a postoperative questionnaire, reinforce the assertions of others, that ketamine is safe and effectively prevents pain in 85 percent of patients. While 13 percent of our patients hallucinated, most found the experience pleasant, and there were no "bad trips" or emergence reactions. Adequate premedication appears to be important in the successful use of ketamine. Whether sedation is augmented with diazepam or achieved with other medications does not appear to matter. A close supportive relationship with the surgeon and operating room personnel is probably as important as any pharmacologic manipulation in avoiding psychological mishap with low-dose ketamine.

Adolescent↗

Inhibition of rabies virus transcription in rat cortical neurons with the dissociative anesthetic ketamine.

In a previous study (B. P. Lockhart, H. Tsiang, P. E. Ceccaldi, and S. Guillemer, Antiviral Chem. Chemother. 2:9-15, 1991), we demonstrated an antiviral effect of the general anesthetic ketamine for rabies virus in neuronal cultures and in rat brain. This report describes an attempt to determine at what level ketamine acts on the rabies virus cycle in rat cortical neuron cultures. Immunofluorescence and [35S]methionine labelling of infected neurons showed that ketamine (1 to 1.5 mM) inhibited viral nucleoprotein and glycoprotein syntheses. Northern (RNA) blots of total RNA from drug-treated neurons, hybridized with 32P-labelled oligonucleotide probes for rabies virus nucleoprotein, matrix protein, and glycoprotein genes, showed a marked reduction (5- to 11-fold) in the levels of rabies virus mRNAs, relative to those in untreated neurons. No significant change in the levels of cellular beta-actin mRNA were detected in ketamine-treated cells. A similar antiviral effect was observed with MK-801; however, no inhibition of rabies virus synthesis was observed with the general anesthetic chloral hydrate. The antiviral effect was not complete; a time-dependent recovery of viral transcription and rabies virus protein synthesis was observed, but no infectious virus was released into the culture supernatant. The lack of any modification of cellular protein or mRNA synthesis by ketamine suggests an antiviral mechanism acting at the level of rabies virus genome transcription.

Animals↗

Use of dissociative anesthetics for the immobilization of captive bears: blood gas, hematology and biochemistry values.

Nineteen bears, representing five species (Helarctos malayanus, Ursus americanus, Ursus arctos, Tremarctos ornatus, Melursus ursinus) were immobilized a total of 52 times using either phencyclidine-promazine or tiletamine-zolazepam. Blood gas, hematology, and serum biochemistry values were determined during the immobilizations. Immobilizations conducted with tiletamine-zolazepam were characterized by rapid induction and recovery times, good muscle relaxation, and relative freedom from convulsions. Bears immobilized with phencyclidine-promazine had longer induction and recovery times and showed convulsive activity in 29% of the trials with that combination.

Animals↗