Subacute benzodiazepine treatment: observations on behavioural tolerance and withdrawal.

The acute and subchronic actions of the benzodiazepines triazolam, oxazepam and diazepam have been examined using three behavioural tests. In the accelerating rotarod motor coordination test both diazepam and oxazepam on acute administration produced dose-related discoordination or motor impairment in mice. After chronic administration (50 mg/kg per day i.p. for 14 days) the corresponding dose-response lines were shifted to the right suggesting tolerance development. In a test for conflict behaviour in rats (conditioned suppression of drinking) oxazepam (20 mg/kg i.p.), triazolam (1 mg/kg i.p.) and diazepam (10 mg/kg i.p.) all augmented punished responding rates with no effect on unpunished responses and this has been speculated to reflect anxiolytic activity. These initial elevations in punished responding displayed a gradual decline during repeated daily administration over 20 days, there being little alteration in the unpunished response levels. In separate studies, chronic treatment of mice with triazolam in the drinking water over 30 days showed diminished pentylenetetrazol-induced seizure latencies compared to the level of protection afforded by triazolam at the beginning of the schedule. In additional experiments, mice injected daily with triazolam (1 mg/kg i.p. for 14 days) exhibited a higher seizure susceptibility than their corresponding controls. The results are discussed in relation to tolerance to the anxiolytic, anticonvulsant and neurological impairment properties of benzodiazepines.