Biol. Pharm. Bull. 29(7) 1414—1417 (2006)

acid (GABA) acting on its type A receptor in the mammalian brain explains the pharmacological and therapeutic actions of benzodiazepines which bind to a specific site in the GABAA receptor. However, the usefulness of benzodiazepines as anxiolytics, sedatives, anticonvulsants and muscle relaxants is compromised by the occurrence of several adverse effects such as ataxia, amnesia, alcohol intolerance, and residual sedation, as well as the related problems of tolerance and dependence after chronic use. Molecular biology studies have established the heterogeneity of GABAA receptors and the pharmacological and electrophysiological study of the different subtypes has allowed the search of new ligands with improved selectivity which eventually may lead to the development of safer drugs. Natural materials including flavonoids have recently attracted interest as new chemical entities with activity on the central nervous system. Many researchers have demonstrated that some naturally-occurring substances possess a selective and relatively mild affinity for the central benzodiazepine binding site in GABAA receptors, and exert selective activities and sedative but not adverse effects. Fossilia Mastodi OSSIS, which is a skeletal fossil of an ancient, extinct mammal, has been reported to have anxiolytic, sedative and anticonvulsant activities in Oriental medicine. It is known to be composed of calcium carbonate, calcium phosphate, trace amounts of Fe, Al and Mg, and 0.03% uranium, and is usually collectable from Shangdong Province and surrounding across in China. In this study, in vivo characterization of the anxiolytic-sedative activities of Fossilia Mastodi OSSIS was carried out in order to obtain basic information on a putative natural sedative.