LOCUS-COERULEUS NORADRENALINE SYSTEM AND FOCAL PENICILLIN HIPPOCAMPALEPILEPSY - NEUROPHYSIOLOGICAL STUDY

Previous experimental investigations have shown that several neuronal systems modulate the spontaneous and paroxysmal electric activity of t he hippocampus. The locus coeruleus-noradrenaline (LC-NA) system exert s an inhibitory influence on several brain areas including the ipsilat eral hippocampus. Selective destruction of the LC increases the suscep tibility to epileptiform phenomena in different models of experimental epilepsy. Our experiments were conducted on 34 rats in which a steady epileptiform interictal activity of the hippocampus was obtained by m eans of intrahippocampal administration of penicillin. Electrical stim ulation of LC caused a significant decrease of penicillin spiking of h ippocampus. Stimulation sessions given 10-15 min after i.p. propranolo l administration (2 mg/kg) failed to induce any significant modificati on in the hippocampal spiking frequency. Intrahippocampal injection of L-noradrenaline mimicked the inhibitory effect of LC electrical stimu lation on hippocampus. Finally, intrahippocampal administration of iso proterenol HCl, a beta-adrenoceptor agonist, caused a significant decr ease of hippocampal penicillin spiking; this effect was antagonised by i.p. propranolol administration. The experimental data show a modulat ing influence of the LC-NA system on penicillin focal hippocampal epil epsy that probably involves beta-adrenoceptars.