Hippocampal FGF-2 and BDNF overexpression attenuates epileptogenesis-associated neuroinflammation and reduces spontaneous recurrent seizures

Under certain experimental conditions, neurotrophic factors may reduce epileptogenesis. We have previously reported that local, intrahippocampal supplementation of fibroblast growth factor-2 (FGF-2) and brain-derived neurotrophic factor (BDNF) increases neurogenesis, reduces neuronal loss, and reduces the occurrence of spontaneous seizures in a model of damage-associated epilepsy. Here, we asked if these possibly anti-epileptogenic effects might involve anti-inflammatory mechanisms. Thus, we used a Herpes-based vector to supplement FGF-2 and BDNF in rat hippocampus after pilocarpine-induced status epilepticus that established an epileptogenic lesion. This model causes intense neuroinflammation, especially in the phase that precedes the occurrence of spontaneous seizures. The supplementation of FGF-2 and BDNF attenuated various parameters of inflammation, including astrocytosis, microcytosis and IL-1β expression. The effect appeared to be most prominent on IL-1β, whose expression was almost completely prevented. Further studies will be needed to elucidate the molecular mechanism(s) for these effects, and for that on IL-1β in particular. Nonetheless, the concept that neurotrophic factors affect neuroinflammation in vivo may be highly relevant for the understanding of the epileptogenic process

Induction of B-1 bradykinin receptors in the kindled hippocampus increases extracellular glutamate levels: A microdialysis study

A link between temporal lobe epilepsy (the most common epileptic syndrome in adults) and neuropeptides has been established. Among neuropeptides, the possible involvement of bradykinin has recently received attention. An autoradiographic analysis has shown that B1 receptors, which are physiologically absent, are expressed at high levels in the rat brain after completion of kindling, a model of temporal lobe epilepsy. Thus, the present work aimed at investigating the functional implications of this observation, by studying the effect of B1 receptor activation on extracellular glutamate levels in the kindled hippocampus. Microdialysis experiments have been performed in two groups of rats, control and kindled. Glutamate outflow has been measured under basal conditions and after chemical stimulation with high K+ (100 mM in the dialysis solution). Basal glutamate outflow in kindled animals was significantly higher than in controls. High K+-evoked glutamate outflow was also more pronounced in kindled animals, consistent with the latent hyperexcitability of the epileptic tissue. The B1 receptor agonist Lys-des-Arg9-BK induced an increase of basal and high K+-evoked glutamate outflow in kindled but not in control rats, and the selective B1 receptor antagonist R-715 prevented both these effects. Furthermore, R-715 significantly reduced high K+-evoked glutamate outflow when applied alone. These data suggest that the bradykinin system contributes to the modulation of epileptic neuronal excitability through B1 receptors

Inhibitory effect of nociceptin on [(3)H]-5-HT release from rat cerebral cortex slices

1. The effect of nociceptin (NC) on 5-hydroxytryptamine (5-HT) release was studied in rat cerebral cortex slices preincubated with [(3)H]-5-HT and electrically stimulated (3 Hz, for 2 min) at the 45th (St(1)) and the 75th (St(2)) min of superfusion. 2. NC (0.1–3 μM), present in the medium from the 70th min onward, concentration-dependently reduced electrically evoked [(3)H]-5-HT efflux (pEC(50)=6.54, E(max) −54%). The inhibition was not antagonized by naloxone (1 μM) ruling out the involvement of opioid receptors. 3. Phe(1)ψ(CH(2)-NH(2))Gly(2)]NC(1-13)NH(2), which acts as an opioid-like receptor (ORL(1)) antagonist at the peripheral level, behaved as a partial agonist in cerebral cortex slices i.e. it inhibited [(3)H]-5-HT efflux when added before St(2), however, when present in the medium throughout the whole experiment, [Phe(1)ψ(CH(2)-NH(2))Gly(2)]NC(1-13)NH(2) prevented the action of NC added at the 70th min. 4. The non-selective ORL(1) receptor antagonist, naloxone benzoylhydrazone (3 μM), in the presence of 10 μM naloxone, did not modify the St(2)/St(1) ratio but completely abolished the NC effect. 5. These findings demonstrate that NC inhibits 5-HT release from rat cerebral cortex slices via ORL(1) receptors, suggesting its involvement in central processes mediated by 5-HT

Localized delivery of fibroblast growth factor–2 and brain-derived neurotrophic factor reduces spontaneous seizures in an epilepsy model

A loss of neurons is observed in the hippocampus of many patients with epilepsies of temporal lobe origin. It has been hypothesized that damage limitation or repair, for example using neurotrophic factors (NTFs), may prevent the transformation of a normal tissue into epileptic (epileptogenesis). Here, we used viral vectors to locally supplement two NTFs, fibroblast growth factor–2 (FGF-2) and brain-derived neurotrophic factor (BDNF), when epileptogenic damage was already in place. These vectors were first characterized in vitro, where they increased proliferation of neural progenitors and favored their differentiation into neurons, and they were then tested in a model of status epilepticus-induced neurodegeneration and epileptogenesis. When injected in a lesioned hippocampus, FGF-2/BDNF expressing vectors increased neuronogenesis, embanked neuronal damage, and reduced epileptogenesis. It is concluded that reduction of damage reduces epileptogenesis and that supplementing specific NTFs in lesion areas represents a new approach to the therapy of neuronal damage and of its consequences

Direct and indirect inhibition by nociceptin/orphanin FQ on noradrenaline release from rodent cerebral cortex in vitro

1. The modulation exerted by nociceptin/orphanin FQ (NC) on noradrenaline (NE) release in rodent cerebral cortex slices and synaptosomes was studied. 2. Rat, mouse and guinea-pig cortical slices and synaptosomes were preincubated with 0.1 μM [(3)H]-NE and superfused. NE release was evoked by 2 min of electrical (3 Hz) stimulation in slices and by 1 min pulse of 10 mM KCl in synaptosomes. 3. In rat cortical slices, 0.01–3 μM NC reduced the evoked [(3)H]-NE efflux (E(max)−54%), with a bell-shaped concentration-response curve, which regained its monotonic nature in the presence of either 0.1 μM naloxone (NX) or 30 μM bicuculline. In synaptosomes, the NC effect curve was sygmoidal in shape and reached a plateau at 1 μM concentration. 4. In the rat, both 1 μM [Phe(1)ψ(CH(2)-NH)Gly(2)]NC(1-13)NH(2) and 10 μM [Nphe(1)]NC(1-13)NH(2) (NPhe) antagonised NC-induced inhibition, without per se modifying [(3)H]-NE efflux. The effects of 0.3–1 μM NC concentrations were partially prevented by 1 μM NX; 1 μM D-Phe-Cys-Thr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP) was also an effective antagonist, but 0.1 μM norbinaltorphimine was not. 5. In the mouse cerebral cortex, NC-induced inhibition of NE release (pEC(50) 6.87, E(max)−61%, in the slices) was prevented by Nphe but was NX-insensitive. In guinea-pig cortical slices, NC effect (pEC(50) 6.22, E(max)−38%) was prevented by Nphe, but was NX-insensitive. 6. These findings demonstrate that NC inhibits NE release from rodent cerebral cortex via presynaptically located ORL(1) receptors. In the rat, μ opioid and GABA(A) receptors are involved as well