CGS 9896: agonist-antagonist benzodiazepine receptor activity revealed by anxiolytic, anticonvulsant and muscle relaxation assessment in rodents.

CGS 9896, a pyrazoloquinoline that potently binds to benzodiazepine receptors, has been reported to have anticonflict activity in conventional footshock paradigms and to antagonize pentylenetetrazol-induced seizures. In the present experiments, the pentylenetetrazol discriminative cue was blocked by CGS 9896 with a potency comparable to that of diazepam. CGS 9896 also selectively lengthened the latency to terminate self-initiated brain stimulation reward. These procedures extend the anxiolytic activity of CGS 9896 to models that do not rely upon footshock-induced conflict. CGS 9896 did not impair the traction reflex in mice, did not impair rotorod performance in rats, did not reduce unpunished operant responding and decreased motor activity only slightly, indicating no distinguishable sedation or muscle relaxation in rodent models. In fact, diazepam-induced rotorod impairment was blocked by CGS 9896. The anticonvulsant effects of CGS 9896, as indicated by audiogenic seizure and pentylenetetrazol-induced seizure studies, were substantial but were weaker than those of diazepam, possibly because of the muscle relaxant component of diazepam. Ethanol-induced motor impairment was potentiated more markedly by diazepam than by CGS 9896. Mixed agonist-antagonist properties of CGS 9896 therefore emerge when a comprehensive battery of behavioral assessments is utilized. CGS 9896 may have clinical anxiolytic activity without sedation or muscle relaxation.