Electrically evoked potentials in the rat hippocampus slice in the presence of aminophylline alone and in combination with quinolones.

The excitability of brain matter was tested bt electrically evoked field potentials in the CA1 region of the rat hippocampus in vitro. In contrast to the quinolones which only increased the amplitudes of electrically evoked potentials, aminophylline induced spontaneous firing in the pyramidal cell layer without stimulation in addition to its dose-dependent effects on the amplitudes of the evoked potentials. Threshold doses of the quinolones tested (0.25 microM) increased the amplitudes of evoked potentials in the presence of an otherwise ineffective concentration of aminophylline (0.5 microM) to different degrees, ranging from 135.3% for ciprofloxacin to 223.8% for nalidixic acid. The rank order of potency of CNS side effects reported in the literature correlates very well with the increase of the population spike amplitude in the hippocampus slice preparation. This feature could be important during the development of new chemical analogues of quinolones.