Bumetanide enhances phenobarbital efficacy in a neonatal seizure model

<jats:title>Abstract</jats:title><jats:sec><jats:title>Objectives</jats:title><jats:p>High levels of expression of the Na<jats:sup>+</jats:sup>‐K<jats:sup>+</jats:sup>‐2Cl<jats:sup>−</jats:sup> (NKCC1) cotransporter in immature neurons cause the accumulation of intracellular chloride and, therefore, a depolarized Cl<jats:sup>−</jats:sup> equilibrium potential (E<jats:sub>Cl</jats:sub>). This results in the outward flux of Cl<jats:sup>−</jats:sup> through GABA<jats:sub>A</jats:sub> channels, the opposite direction compared with mature neurons, in which GABA<jats:sub>A</jats:sub> receptor activation is inhibitory because Cl<jats:sup>−</jats:sup> flows into the cell. This outward flow of Cl<jats:sup>−</jats:sup> in neonatal neurons is excitatory and contributes to a greater seizure propensity and poor electroencephalographic response to GABAergic anticonvulsants such as phenobarbital and benzodiazepines. Blocking the NKCC1 transporter with bumetanide prevents outward Cl<jats:sup>−</jats:sup> flux and causes a more negative GABA equilibrium potential (E<jats:sub>GABA</jats:sub>) in immature neurons. We therefore tested whether bumetanide enhances the anticonvulsant action of phenobarbital in the neonatal brain</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Recurrent seizures were induced in the intact hippocampal preparation in vitro by continuous 5‐hour exposure to low‐Mg<jats:sup>2+</jats:sup> solution. The anticonvulsant efficacy of phenobarbital, bumetanide, and the combination of these drugs was studied</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Phenobarbital failed to abolish or depress recurrent seizures in 70% of hippocampi. In contrast, phenobarbital in combination with bumetanide abolished seizures in 70% of hippocampi and significantly reduced the frequency, duration, and power of seizures in the remaining 30%</jats:p></jats:sec><jats:sec><jats:title>Interpretation</jats:title><jats:p>Thus, alteration of Cl<jats:sup>−</jats:sup> transport by bumetanide enables the anticonvulsant action of phenobarbital in immature brain. This is a mechanistic demonstration of rational anticonvulsant polypharmacy. The combination of these agents may comprise an effective therapy for early‐life seizures. Ann Neurol 2007</jats:p></jats:sec>