[Blood-brain barrier--an important factor for distribution of hypnotics and their metabolites in the central nervous system].

It can be assumed, that the morphological structures of the blood-brain-barrier (BBB) and blood-cerebrospinal fluid-barrier (BCB) are built at the same principle and stops considerably the transport of water soluble substances to the cells of the brain. To these belong polar groups of active substances, which improve their water solubility (OH-, COOH-, CO-, NH2- and SH-substitutes). On the other side lipophilic solvents as vehicles support the penetration of such polar substances into the brain. Our aim in this paper was to investigate the distribution of unchanged barbiturates and their polar metabolites in the brain within the scope of animal experiments. All the animals (cats) got an overdose of Pentobarbital, to which a small quantity of the hypnotic marked with a 14C atom was added. Pentobarbital metabolizes in the organism in short times to hydroxy- and carboxy-pentobarbital. After different times of killing the organs and body fluids, especially the brain were examined and the results compared. It could be shown that in the brain of all animals in spite of different killing times 75-90 per cent of the unchanged barbiturate has been found. On the other side, only a maximum of 20 per cent of the pentobarbital metabolites was found in the brain cells. In the other organs and body fluids the part of the unchanged barbiturate was much lower, between 10 and 50 per cent, depending on the killing time. The quantity of the metabolites was essential higher, with variations between 50 and 90 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)