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Pharmacodynamic and pharmacokinetic actions of ketocyclazocine enantiomers in the dog: absence of sigma- or phencyclidine-like activity.

Authors
  • Vaupel, D B
  • Cone, E J
Type
Published Article
Journal
The Journal of pharmacology and experimental therapeutics
Publication Date
Jan 01, 1991
Volume
256
Issue
1
Pages
211–221
Identifiers
PMID: 1846414
Source
Medline
License
Unknown

Abstract

The effects of the optical isomers and the racemic form of ketocyclazocine (KC) were compared with morphine and U-50,488H in the chronic spinal dog. l-KC and dl-KC produced depression of nociceptive reflexes, miosis, relaxation of the nictitating membrane and sedation, whereas d-KC lacked pharmacological activity. Peak plasma levels and distribution phase half-lives for dl-, l- and d-KC were similar, indicating no major dispositional differences between the isomers of KC despite a trend for d-KC to have a longer elimination half-life, slower plasma clearance and a greater apparent volume of distribution than l-KC. Although a relatively low dose of naltrexone (0.01 mg/kg) was sufficient to shift morphine dose-effect curves to the right, this dose of naltrexone was not sufficient to shift the dose-effect curves of dl-KC to the right. A dose of 1 mg/kg of naltrexone was required, consistent with the view that the effects were mediated by kappa opioid receptors. The overall pharmacological profile of l-KC differed from that of the more selective kappa opioid agonist U-50,488H, which produced both stimulatory and sedative effects. Neither l-KC nor U-50,488H produced pharmacological profiles typical of the sigma agonist d-N-allylnormetazocine or phencyclidine. The data suggest that the pharmacological activity of KC resides in the l-enantiomer, that the effects are kappa opioid receptor-mediated and that the binding of d-KC to haloperidol-sensitive sigma receptors does not produce N-allylnormetazocine- or phencyclidine-like actions in the dog.

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