Midazolam-induced increase in NaCl solution ingestion: differential effect of the benzodiazepine antagonists Ro 15-1788 and CGS 8216.

After adaptation to a 23-hr water deprivation regimen, under which rats were allowed a daily 1-hr water rehydration session, they were injected (SC) with 1 or 2 drugs presession and given 1.5% NaCl solution to drink in place of water. Midazolam (0.5-1.0 mg/kg) increased the intake of 1.5% NaCl solution as did Ro 15-1788 (2.5-10.0 mg/kg). This confirmed a previously noted agonist effect of midazolam and partial agonist action of Ro 15-1788. When injected in combination with midazolam, Ro 15-1788 (2.5-10.0 mg/kg) antagonized the effect of midazolam. CGS 8216 (2.5-20.0 mg/kg) revealed no partial agonist action on the NaCl solution ingestion procedure nor did it block the effect of midazolam.