γ-Hydroxybutyrate (GHB) is an emerging drug of abuse with multiple mechanisms of action. This study is part of an effort to examine the role of GHB, GABAA, and GABAB receptors in the discriminative stimulus (DS) effects of GHB. In pigeons trained to discriminate 100 mg/kg GHB from saline, GHB and its precursors γ-butyrolactone and 1,4-butanediol produced 80 to 100% GHB-appropriate responding, whereas other compounds such as morphine, naltrexone, cocaine, and haloperidol produced no more than 34%. Compounds interacting with GABA receptors produced different maximal levels of GHB-appropriate responding. For example, the GABAA agonist muscimol produced 3%; the GABAA-positive modulators diazepam, pentobarbital, and ethanol, and the GABAB agonist baclofen produced levels ranging from 54 to 73%; and the benzodiazepine antagonist flumazenil and inverse agonist Ro 15-4513 (ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-α]-[1,4] -benzodiazepine-3-carboxylate) both produced 96%. The putative GHB receptor antagonist (2E)-(5-hydroxy-5,7,8,9-tetrahydro-6H-benzo[a]annulen-6-ylidene ethanoic acid (NCS-382) produced 70% GHB-appropriate responding. The GABA B antagonist (3-aminopropyl)(diethoxymethyl)phosphinic acid (CGP 35348) completely blocked the GHB-like DS effects of NCS-382 and baclofen at a dose of 56 mg/kg. CGP 35348 also blocked the DS effects of GHB, but incompletely and only at a dose of 560 mg/kg. Together, these results are consistent with a role for diazepam-sensitive and -insensitive GABAA and GABAB receptors in the DS effects of GHB. Together with previous findings, the present results suggest that diazepam-insensitive GABA A receptors are more prominently involved in the DS effects of GHB in pigeons than in rats, whereas GABAB receptors are less prominently involved. Exploring the role of GHB receptors with NCS-382 is hampered by its GABAB receptor-mediated, GHB-like agonist activity.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - Mar 2004|
ASJC Scopus subject areas
- Molecular Medicine