The role of delta opioid receptors in the anxiolytic actions of benzodiazepines.
The anxiolytic effects of benzodiazepines appear to involve opioid processes in the amygdala. In previous experiments, overexpression of enkephalin in the amygdala enhanced the anxiolytic actions of the benzodiazepine agonist diazepam in the elevated plus maze. The effects of systemically administered diazepam are also blocked by injections of naltrexone into the central nucleus of the amygdala. The current studies investigated the role of delta opioid receptors in the anxiety-related effects of diazepam. Three days following bilateral stereotaxic injections of viral vectors containing cDNA encoding proenkephalin or beta-galactosidase (control vector), the delta opioid receptor antagonist naltrindole (10 mg/kg, s.c.) attenuated the enhanced anxiolytic effects of 1-2 mg/kg diazepam in rats overexpressing preproenkephalin in the amygdala. Despite this effect, naltrindole failed to attenuate the anxiolytic action of higher diazepam doses (3 mg/kg) in animals with normal amygdalar enkephalin expression. Similarly, the mu opioid receptor antagonist, beta-funaltrexamine (20 mg/kg, s.c.), had no effect on the anxiolytic effect of diazepam alone. These data support a role for delta opioid receptors in the opioid-enhanced anxiolytic effects of diazepam.
Primeaux
Stefany D
SD
Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Bldg 1, Columbia, SC 29208, USA.
Wilson
Steven P
SP
McDonald
Alexander J
AJ
Mascagni
Franco
F
Wilson
Marlene A
MA
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001569:Benzodiazepines / Q000494:pharmacology*; D003975:Diazepam / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D017465:Receptors, Opioid, delta / Q000502:physiology*
D014151:Anti-Anxiety Agents; D004745:Enkephalins; D011963:Receptors, GABA-A; D017465:Receptors, Opioid, delta; D001569:Benzodiazepines; D009271:Naltrexone; C024524:beta-funaltrexamine; C055382:naltrindole; D003975:Diazepam