Antagonists of benzodiazepines

Benzodiazepines (BDZ) interact with specific receptors (R), whose activation improves Cl- -channel gating by the GABA receptor (GABA-R). Neurones, whose GABAergic input has a certain level of activity, will be more inhibited in the presence of BDZ (primary target neurones for BDZ). Secondarily, neurones dependent on the activity of primary target neurones will also be effected. Drugs that interact with GABAergic functions (except the BDZ-R) or with the function of primary or secondary target neurones may inhibit some or all BDZ effects; these are nonspecific BDZ antagonists (e.g. GABA-antagonists, cholinesterase inhibitors, naloxone, methylxanthines). Specific BDZ antagonists inhibit the action of BDZ by blocking competitively the BDZ-R. Ro 15-1788 is the best investigated specific BDZ antagonist. Virtually devoid of any pharmacological action by itself, the compound blocks all typical effects of BDZ. It is well tolerated also in man and will find application in anaesthesiology to shorten the sedative and muscle relaxant effect of BDZ and in emergency services to reverse comatose states after BDZ overdosage. Recently drugs have been found that produce effects opposite to the BDZ tranquilizers by inducing a conformation of the BDZ-R which depresses GABA-mediated Cl- -channel gating. The effects of these inverse agonists (e.g. proconvulsant , convulsant, anxiogenic) are blocked by pure competitive BDZ-R blockers, such as Ro 15-1788.