Chronic administration of benzodiazepines--V. Rapid onset of behavioral and neurochemical alterations after discontinuation of alprazolam.

Discontinuation of chronic treatment with alprazolam may cause a characteristic clinical syndrome. To assess the basis of this syndrome, mice were treated with alprazolam, 2 mg/kg, for 7 days, a regimen associated with the development of tolerance and downregulation of receptors. Effects on motor activity and the binding and function of GABA receptors were evaluated 1, 2, 4 and 7 days after discontinuation. Motor activity was similar to controls 1 day after cessation of alprazolam, increased from days 2 to 4 after-alprazolam, and returned to control values by 7 days. The binding of benzodiazepines in vivo and in vitro was increased in the cortex 2 and 4 days after alprazolam and in the hypothalamus at 4 days after alprazolam. Binding returned to control values in all areas by 7 days. Binding at the chloride channel, using [35S]t-butylbicyclophosphorothionate, was not significantly altered after discontinuation. Muscimol-stimulated uptake of [36Cl-] in cortical synaptoneurosomes was increased at 4 days after alprazolam, compared to days 1, 2 and 7. Thus, behavioral and neurochemical alterations was associated with the discontinuation of alprazolam. These alterations were qualitatively similar to those observed following discontinuation of lorazepam but occurred more rapidly and with differing regional specificity.