| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1991: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1990: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
1. Interactions of quinolone antibiotics and non-steroidal anti-inflammatory drugs(NSAIDs)with the y-aminobutyric acid-A(GABA_A)receptor-chloride channel complex in pyramidal neurons freshly dissociated from the hippocampal CAl region of rats were investigated in whole cell mode, using the patch-clamp technique under voltage-clamp conditions.
2. Quinolones in clinical doses had no effects on 5the GABA-gated Cl^- current(I_<C1>)but slightly suppressed the response at concentrations over 10^<-5> M. A metabolite of fenbufen, 4-biphenylacetic acid(BPA, one of NSAIDs)itself, also had little effect on the GABA response at therapeutic concentrations.
3. Coadministraiton of one of quinolones and BPA markedly suppressed the GABA-gated I with increase in each of them in a concentration-dependent manner. There was a parallel shift of the concentration-response curve for GABA to the right but with no effect on the maximum response, indicating a competitive antagonism. The inhibitory potency of antibiotics in combination with BPA was in the order of norfloxacin>>enoxacm>cyprofloxacin>pipemidic acid>>ofloxacin>cinoxacin = piromidic acid = nalidixic acid = 0.
4. In the presence of norfloxacin(NFLX), one of quinolones, some NSAIDs suppressed the GABA response in a concentration-dependent manner. The inhibitory potency of NSAISs was BPA>>indomethacin = naproxen>mefenamic acid>diclofenac>piroxicarn.
5. It was concluded that, in the presence of an anti-inflammatory agent(BPA), the quinolone antibiotics decrease the affinity of GABA_A receptors. And, in the presence of a quinolone(NFLX), BPA, indomethacin and naproxen may induce the epileptogenic neurotoxicities via pharmacological interaction with GABA_A receptor.
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