Tolerance and dependence following chronic alprazolam treatment in rhesus monkeys: Role of GABA A receptor subtypes

• Published in: Drug and alcohol dependence 2021-11, Vol.228, p.108985
• Main Authors: Duke, Angela N, Tiruveedhula, V V N Phani Babu, Sharmin, Dishary, Knutson, Daniel E, Cook, James M, Platt, Donna M, Rowlett, James K
• Format: Article
• Language: English
• Subjects: Alprazolam - pharmacology; Animals; Benzodiazepines; Drug Tolerance; Female; Macaca mulatta; Midazolam - pharmacology; Receptors, GABA-A - classification; Substance Withdrawal Syndrome; Zolpidem
• ISSN: 1879-0046
• DOI: 10.1016/j.drugalcdep.2021.108985

To assess GABA receptor subtypes involved in benzodiazepine tolerance and dependence, we evaluated the ability of subtype-selective and non-selective ligands to substitute for (i.e., produce "cross-tolerance") or precipitate withdrawal during chronic alprazolam treatment. Four female rhesus monkeys (Macaca mulatta) were implanted with chronic intravenous catheters and administered alprazolam (1.0 mg/kg every 4 h). Following 14+ days of chronic alprazolam, acute administration of selected doses of non-selective and subtype-selective ligands were substituted for, or administered with, alprazolam, followed by quantitative behavioral observations. The ligands included alprazolam and midazolam (positive modulators, non-selective), zolpidem (positive modulator, preferential affinity for α1-containing GABA receptors), HZ-166 (positive modulator, preferential efficacy at α2- and α3-containing GABA receptors), and βCCT (antagonist, preferential affinity for α1-containing GABA receptors). Acutely, alprazolam and midazolam both induced observable ataxia along with a mild form of sedation referred to as "rest/sleep posture" at a lower dose (0.1 mg/kg, i.v.), whereas at a higher dose (1.0 mg/kg, i.v.), induced deep sedation and observable ataxia. With chronic alprazolam treatment, observable ataxia and deep sedation were reduced significantly, whereas rest/sleep posture was unchanged or emerged. Zolpidem showed a similar pattern of effects, whereas no behaviors engendered by HZ-166 were changed by chronic alprazolam. Administration of βCCT, but not HZ-166, resulted in significant withdrawal signs. These results are consistent with a role for α1-containing GABA receptor subtypes in tolerance and dependence observed with chronic alprazolam, although other receptors may be involved in the withdrawal syndrome.