Neurosteroid coadministration prevents development of tolerance and augments recovery from benzodiazepine withdrawal anxiety and hyperactivity in mice.

Neurosteroids are potent and specific modulators of the GABAA receptors which regulate the neuronal activity through diverse neurotransmitter mechanisms. In the present study we investigated the effects of concomitant treatment with various neurosteroids on the development of tolerance and recovery from withdrawal anxiety and hyperactivity to chronic benzodiazepines. Long-term treatment of mice with full allosteric modulator (triazolam 0.25 mg/kg/day for 8 days) or selective allosteric modulator (diazepam 20 mg/kg/day for 21 days) of GABAA receptor induced tolerance to behavioral sedation on actimeter and anxiolytic effects on plus-maze, and produced a marked withdrawal anxiety and hyperactivity syndrome upon abrupt cessation of treatment, respectively. Concomitant progesterone (10 mg/kg, s.c.), a neurosteroid precursor, of 4'-chlordiazepam (0.25 mg/kg, i.p.), a mitochondrial diazepam binding inhibitor (DBI) receptor (MDR) ligand, prevented the development of tolerance and significantly augmented the recovery from withdrawal-induced anxiety and hyperlocomotion to diazepam. When administered alone for 21 days, neither progesterone nor 4'-chlordiazepam produced any per se effects on actimeter or plus-maze when tested on post-withdrawal days. Coadministration of neurosteroid allopregnanolone (AP) (0.25 and 0.5 mg/kg), or pregnenolone sulfate (PS) (2 mg/kg), but not dehydroepiandrosterone sulfate (2 mg/kg), abolished the development of tolerance and attenuated withdrawal-induced anxiety and hyperlocomotion due to triazolam, without producing any per se behavioral effects when tested at 1 and 2 days after the last injection. Coadministration of flumazenil (5 mg/kg), progesterone (10 mg/kg), 4'-chlordiazepam (0.25 mg/kg), hydrocortisone (100 mg/kg) or nifedipine (2 mg/kg) also prevented the development of tolerance and suppressed the triazolam withdrawal syndrome. However, pretreatment with PK11195 (2 mg/kg), a MDR partial antagonist, reversed the effects of 4'-chlordiazepam on triazolam tolerance and recovery from chronic triazolam. When injected simultaneously, nifedipine, a Ca2+ channel antagonist, potentiated the progesterone- and 4'-chlordiazepam-induced attenuation of triazolam tolerance and withdrawal behavior. These findings suggest that coadministration of neurosteroids allopregnanolone, pregnenolone sulfate and progesterone, and MDR ligand 4'-chlordiazepam prevents the development of tolerance to benzodiazepines and augments the recovery from chronic benzodiazepines. These results indicate that coadministration of neurosteroids may facilitate discontinuation of benzodiazepines in long-term therapy.