Changes in benzodiazepine receptors by acute stress: different effect of chronic diazepam or RO 15-1788 treatment.

In rats submitted to acute stress by forced swimming there was an immediate sharp decline in the binding of [3H]flunitrazepam and of [3H]ethyl-beta-carboline-3-carboxylate in synaptosomal membranes of the cerebral cortex and hippocampus. This was followed by a rebound increase in benzodiazepine receptors after 60 min, specially in the hippocampal formation. These two changes were blocked by chronic treatment with diazepam for 14 days (4 mg/kg/day). On the other hand, long-term treatment with the antagonist RO 15-1788 did not modify the changes caused by the acute stress. These findings are discussed in relation to the possible regulation of benzodiazepine receptors by agonists and antagonists.