Selected Publications
- Feuerstein TJ, Limberger N (1999) Mathematical analysis of the control of neurotransmitter release by presynaptic receptors as a supplement to experimental data. Naunyn-Schmiedeberg´s Arch Pharmacol 359:349-359
- Stefan H, Feuerstein TJ (2007) Novel anticonvulsant drugs. Pharmacol Ther 113:165-183
- Feuerstein TJ (2008) Presynaptic receptors for dopamine, histamine and serotonin.Handb Exp Pharmacol 184:289-338
- Feuerstein TJ, Kammerer M, Lücking CH, Moser A (2011) Selective GABA release as a mechanistic basis of high frequency stimulation used for the treatment of neuropsychiatric diseases. Naunyn-Schmiedberg´s Arch Pharmacol 384:1-20
- Rassner MP, van Velthoven-Wurster V, Ramantani G, Feuerstein TJ (2013) Altered transporter-mediated neocortical GABA release in Rasmussen encephalitis. Epilepsia 54(3):e41–e44
FRIAS Project
Transporter-mediated GABA release as endogenous anti-seizure defense mechanism.
The human brain is predisposed to epileptic seizures under certain circumstances. Fortunately, endogenous anti-seizure mechanisms usually prevent such seizures. One of the most important mechanisms in this regard is transporter-mediated GABA release. The notion that synaptic transmission occurs solely by exocytosis is definitely not the case for GABA neurons. Transporter-mediated GABA release happens, for instance, when neurons are robustly depolarized due to repetitive influx of Na+ as occurs during epileptic seizures.
We characterized veratridine-evoked 3H-GABA release from human neocortical synaptosomes as caused solely by transporter reversal due to both depolarization and increased cytosolic Na+ ([Na+]i). Surprisingly, removal of extracellular Ca2+ ([Ca2+]e) increased this release, most probably by activating the synaptosomal Na+/Ca2+ exchanger (NCX) which further elevated [Na+]i and thus enhanced veratridine-induced transporter reversal. Increased GABA release due to decreased [Ca2+]e may counteract paroxysmal activity as lowering [Ca2+]e can induce spreading epileptiform activity.
My FRIAS project will investigate this anti-seizure defense mechanism in synaptosomes and in slices of human and rat neocortex. Methods are synaptosomal GABA release and patch-clamp analysis of pyramidal cells and GABAergic interneurons. The pre- and postsynaptic NCX will be analyzed at different [Ca2+]e to determine whether NCX modulation provides an antiepileptic target of possible clinical relevance. Specifically, a NCX-activating drug may offer a new anticonvulsant mechanism having a favorable side effect profile; i.e., this drug would selectively enhance (quasi-physiologically) an endogenous antiepileptic process, even more so when applied locally to ameliorate a seizure focus, yet not alter peripheral processes (e.g., cardiovascular).