Structure-epileptogenicity relationship of quinolones with special reference to their interaction with gamma-aminobutyric acid receptor sites.
The relationship between the chemical structure and epileptogenic activity of quinolones was investigated. When the quinolones were administered intravenously to mice concomitantly with oral biphenylacetic acid, a major metabolite of the nonsteroidal antiinflammatory drug fenbufen, enoxacin, norfloxacin, ciprofloxacin, and pipemidic acid, which have an unsubstituted piperazine moiety at the 7 position of their parent nuclei, provoked clonic convulsions and subsequent death at doses of 6.25 mg/kg or more in a dose-dependent manner. AM-1091 and T-3262, which have an unsubstituted aminopyrrolidine moiety at their 7 positions, were less epileptogenic than the compounds listed above were. In contrast, ofloxacin, AT-4140, and nalidixic acid, which have piperazine substituted with methyl group(s) or no piperazine moiety at their 7 positions, never induced convulsions, even at doses of 100 mg/kg. Lomefloxacin, which has a 3-methyl piperazine, however, provoked convulsions at doses of 6.25 mg/kg or more. In the presence of biphenylacetic acid, all the test quinolones except nalidixic acid competitively inhibited [3H]muscimol binding to receptor sites for gamma-aminobutyric acid (GABA) in vitro. Nalidixic acid did not inhibit the binding at all, even at the highest concentration tested, i.e., 10(-4) M. The 50% inhibition doses for [3H]muscimol binding varied within 4 orders of magnitude or more, between 10(-8) to more than 10(-4) M for various compounds, and there was a close correlation between the epileptogenic activities of quinolones and their inhibitory potencies for [3H]muscimol binding to GABA receptor sites. These results indicate that the epileptogenic activity of quinolones possibly relates to the GABA-like structures of substituents at their 7 positions, which act as antagonists of GABA receptors.
Akahane
K
K
Research Institute, Daiichi Pharmaceutical Co., Ltd., Tokyo, Japan.
Sekiguchi
M
M
Une
T
T
Osada
Y
Y
D042462:4-Quinolones; D000818:Animals; D000890:Anti-Infective Agents / Q000378:metabolism / Q000633:toxicity*; D001923:Brain Chemistry / Q000187:drug effects; D004827:Epilepsy / Q000139:chemically induced*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009118:Muscimol / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism; D013329:Structure-Activity Relationship; D013570:Synaptic Membranes / Q000378:metabolism
D042462:4-Quinolones; D000890:Anti-Infective Agents; D011963:Receptors, GABA-A; D009118:Muscimol