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Psychopharmacology (Berl). 2002 Aug;163(1):111-7. Epub 2002 Jun 27.

Involvement of the opioid system in the anxiolytic-like effects induced by Delta(9)-tetrahydrocannabinol.

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  • 1Laboratori de Neurofarmacologia, Facultat de CiĆ©ncies de la Salut i de la Vida, Universitat Pompeu Fabra, C/Doctor Aiguader 80, 08003 Barcelona, Spain.

Abstract

RATIONALE:

Recent studies have shown that several pharmacological actions induced by cannabinoids, including antinociception and reward, involve the participation of the endogenous opioid system.

OBJECTIVES:

The present study was designed to examine the possible involvement of the different opioid receptors in the anxiolytic-like responses induced by Delta(9)-tetrahydrocannabinol (THC).

METHODS:

The administration of a low dose of THC (0.3 mg/kg) produced clear anxiolytic-like responses in the light-dark box, as previously reported. The effects of the pretreatment with the CB(1) cannabinoid receptor antagonist, SR 141716A (0.5 mg/kg), or the micro -opioid receptor antagonist, beta-funaltrexamine (5 mg/kg), the delta-opioid receptor antagonist, naltrindole (2.5 mg/kg) and the kappa-opioid receptor antagonist, nor-binaltorphimine (2.5 mg/kg) were evaluated on anxiolytic-like responses induced by THC.

RESULTS:

SR 141716A completely blocked the anxiolytic-like response induced by THC, suggesting that this effect is mediated by CB(1) cannabinoid receptors. The micro -opioid receptor antagonist beta-funaltrexamine and the delta-opioid receptor antagonist naltrindole, but not the kappa-opioid receptor antagonist nor-binaltorphimine, abolished THC anxiolytic-like effects, suggesting an involvement of micro - and delta-opioid receptors in this behavioural response.

CONCLUSIONS:

These results demonstrate that the endogenous opioid system is involved in the regulation of anxiety-like behaviour by cannabinoids and provide new findings to clarify further the interaction between these two neuronal systems.

PMID:
12185408
[PubMed - indexed for MEDLINE]
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