RO5-4864, a ligand for benzodiazepine micromolar and peripheral binding sites: antagonism and enhancement of behavioural effects.

RO5-4864, a ligand for both the peripheral and for the central nervous system micromolar benzodiazepine binding sites, was investigated in the holeboard, alone and in combination with several other drugs. RO5-4864 alone caused a marked reduction in rears and motor activity and reduced head-dipping when objects were placed under the holes. All these reductions were enhanced by picrotoxin (2 and 4 mg/kg) and by CGS 8216 (3 mg/kg). RO15-1788 (10 mg/kg) reversed the reduction in rears and PK11195 (30 mg/kg), a putative antagonist for the peripheral binding site, reversed the reduction in head-dipping. The results are discussed in terms of the various benzodiazepine binding sites and possible non-specific drug effects.