The effects induced by the sulphonylurea glibenclamide on the neonatal rat spinal cord indicate a novel mechanism to control neuronal excitability and inhibitory neurotransmission

Abstract

Background and purpose: Using the neonatal rat spinal cord in vitro, we investigated the action of glibenclamide, a drug possessing dual pharmacological effects, namely block of K ATP channels and of the cystic fibrosis transmembrane conductance regulator (CFTR). Experimental approach: Intra-and extracellular recordings were performed on motoneurons and interneurons. RT-PCR and western immunoblotting were used to determine gene and protein expression. Key results: Glibenclamide (50 mM) facilitated mono-and polysynaptic reflexes, hyperpolarized motoneuron resting potential, increased action potential amplitude, decreased Renshaw cell-mediated recurrent inhibition, and increased network excitability by depressing GABA-and glycine-mediated transmission. The action of glibenclamide was mimicked by tolbutamide (500 mM) or the CFTR blocker diphenylamine-2,2-dicarboxylic acid (500 mM). The action of glibenclamide was independent from pharmacological inhibition of the Na þ -K þ pump with strophanthidin (4 mM) and was associated with a negative shift in the extrapolated reversal potential for CI -dependent synaptic inhibition. On interneurons, intracellularlyapplied 8-bromo-cAMP elicited an inward current and resistance decrease; effects antagonized by the selective CFTR antagonist, CFTR inh -172 (5 mM). RT-PCR and western immunoblotting indicated strong expression of the CFTR in neonatal rat spinal cord. Conclusions and implications: These data suggest the CFTR expressed in motoneurons and interneurons of the neonatal spinal cord is involved in the control of Cl -homeostasis and neuronal excitability. CFTR appeared to contribute to the relatively depolarized equilibrium potential for synaptic inhibition, an important process to control hyperexcitability and seizurepredisposition in neonates.

Cystic fibrosis transmembrane conductance regulator modulates synaptic chloride homeostasis in motoneurons of the rat spinal cord during neonatal development

“…Glibenclamide produced motoneuron resistance increase and membrane hyperpolarization consistent with the inhibition of a background outward conductance that was comparatively similar at P1 and P8. Our previous investigation has shown changes in passive membrane motoneuron properties produced by glibenclamide to be readily accounted by inhibition of a CFTR-dependent background conductance (Ostroumov, 2007;Ostroumov et al, 2007). Assuming that this effect of glibenclamide is due to inhibition of CFTR which is already largely expressed at somatic level of motoneurons even at P1, we may suggest that there is a CFTR-modulated leak inward conductance that regulates the basic somatic properties.…”

“…However, CFTR expression in nonepithelial cells like macrophages, lymphocytes, neutrophils, and smooth muscle cells has been reported (Fonknechten et al, 1992;Di et al, 2006;Painter et al, 2006;Vandebrouck et al, 2006). Although CFTR expression has been found in neurons of the central nervous system (Mulberg et al, 1994;Ostroumov et al, 2007;Guo et al, 2009), its role remains unclear.…”

A new stochastic tridimensional model of neonatal rat spinal motoneuron for investigating compartmentalization of neuronal conductances and their influence on firing

“…The motoneuron morphology is shown in Fig. 5a, while somatic R m was drastically decreased (166 cm 2 ) to simulate sharp electrode penetration with resultant fall of input resistance to 22 M as often observed (Ostroumov et al, 2007), while antidromic action potentials could still be successfully generated.…”

“…Our recent study (Ostroumov et al, 2007) suggested the expression of cystic fibrosis transmembrane conductance regulator (CFTR) in neonatal rat spinal motoneurons. Application of CFTR antagonists like glibenclamide increased input resistance and spike overshoot.…”

Cystic Fibrosis Transmembrane Conductance Regulator Protein (CFTR) Expression in the Developing Human Brain

“…Even if these symptoms may result from a complex association of diabetes, autoimmunity and vitamin deficiency, a primary CFTR defect is also likely to be involved as shown by the recent report of peripheral nervous system defects observed in CFTR -/-pigs at birth (Reznikov et al 2013). Concerning CFTR protein function, recent works have studied CFTR activity in motor neurons of the spinal cord or brainstem nuclei in rats during neonatal development (Ostroumov et al 2007;Morales et al 2011) and have shown that CFTR contributes to the relatively depolarized equilibrium potential for synaptic inhibition, an important process to control hyperexcitability and seizure-predisposition in neonates (Ostroumov et al 2007). It has also been shown that CFTR plays a role in postsynaptic inhibition of motor neurons from the trigeminal motor nucleus during rapid-eye-movement (REM) sleep (Morales et al 2011).…”