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Brigidi GS, Hayes MGB, Delos Santos NP, Hartzell AL, Texari L, Lin PA, Bartlett A, Ecker JR, Benner C, Heinz S, Bloodgood BL. Genomic Decoding of Neuronal Depolarization by Stimulus-Specific NPAS4 Heterodimers. Cell 2019; 179:373-391.e27. [PMID: 31585079 PMCID: PMC6800120 DOI: 10.1016/j.cell.2019.09.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 07/22/2019] [Accepted: 09/04/2019] [Indexed: 12/14/2022]
Abstract
Cells regulate gene expression in response to salient external stimuli. In neurons, depolarization leads to the expression of inducible transcription factors (ITFs) that direct subsequent gene regulation. Depolarization encodes both a neuron's action potential (AP) output and synaptic inputs, via excitatory postsynaptic potentials (EPSPs). However, it is unclear if distinct types of electrical activity can be transformed by an ITF into distinct modes of genomic regulation. Here, we show that APs and EPSPs in mouse hippocampal neurons trigger two spatially segregated and molecularly distinct induction mechanisms that lead to the expression of the ITF NPAS4. These two pathways culminate in the formation of stimulus-specific NPAS4 heterodimers that exhibit distinct DNA binding patterns. Thus, NPAS4 differentially communicates increases in a neuron's spiking output and synaptic inputs to the nucleus, enabling gene regulation to be tailored to the type of depolarizing activity along the somato-dendritic axis of a neuron.
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Affiliation(s)
- G Stefano Brigidi
- Division of Biological Sciences, Section of Neurobiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Michael G B Hayes
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Nathaniel P Delos Santos
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA; Department of Biomedical Informatics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Andrea L Hartzell
- Division of Biological Sciences, Section of Neurobiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA; Neuroscience Graduate Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Lorane Texari
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Pei-Ann Lin
- Division of Biological Sciences, Section of Neurobiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA; Neuroscience Graduate Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Anna Bartlett
- Genomic Analysis Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Joseph R Ecker
- Genomic Analysis Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA; Howard Hughes Medical Institute, La Jolla, CA 92093, USA
| | - Christopher Benner
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Sven Heinz
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
| | - Brenda L Bloodgood
- Division of Biological Sciences, Section of Neurobiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA.
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Yoshida I, Monji A, Hashioka S, Ito M, Kanba S. Prophylactic effect of valproate in the treatment for siblings with catatonia: a case report. J Clin Psychopharmacol 2005; 25:504-5. [PMID: 16160635 DOI: 10.1097/01.jcp.0000177850.23534.69] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Martín ED, Pozo MA. Valproate reduced excitatory postsynaptic currents in hippocampal CA1 pyramidal neurons. Neuropharmacology 2004; 46:555-61. [PMID: 14975679 DOI: 10.1016/j.neuropharm.2003.10.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2003] [Revised: 07/24/2003] [Accepted: 09/11/2003] [Indexed: 12/21/2022]
Abstract
Valproate (VPA) is one of the most widely used antiepileptic drugs, and it is also increasingly used for the treatment of neuropsychological disorders and neuropathic pain, as well as migraine prophylaxis. However, the underlying cellular mechanisms of VPA on the synaptic physiology remain unclear. We investigated the effects of VPA on synaptic transmission using the in vitro rat hippocampal slice technique and whole-cell patch clamp recordings from CA1 pyramidal neurons. Perfusion with VPA, at therapeutically attainable concentrations, decreased the amplitude of excitatory postsynaptic currents (EPSCs) evoked by Schaffer collateral stimulation, without modifying inhibitory postsynaptic currents (IPSCs). Furthermore, VPA induced a significant reduction of the non-NMDA EPSC (non-NMDA(EPSC)) component, without modifying the NMDA EPSC (NMDA(EPSC)) component. Paired pulse facilitation and EPSC variance were not significantly affected by VPA, indicating that VPA did not decrease transmitter release probability, which suggests a postsynaptic mechanism of action. We therefore conclude that VPA decreases excitatory synaptic activity through the modulation of postsynaptic non-NMDA receptors, without modifying synaptic inhibition, and that this reduction of excitation is, at least in part, responsible for the effects of VPA.
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Affiliation(s)
- Eduardo D Martín
- Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Avda Almansa s/n, 02071 Albacete, Spain.
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Shahar E, Andraus J, Sagie-Lerman T, Savitzki D. Valproic acid therapy inducing absence status evolving into generalized seizures. Pediatr Neurol 2002; 26:402-4. [PMID: 12057805 DOI: 10.1016/s0887-8994(01)00413-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The authors herein present two children with mild absence epilepsy, having intermittent absences, who developed absence status evolving into atonic generalized seizures and drop attacks along with progressive disorientation induced by relatively small doses of valproic acid. Consciousness and awareness were intact before the introduction of valproic acid. Both children, after the first dose of valproic acid, developed prolonged and recurrent clusters of absences, which became prolonged, with drop attacks occurring in one patient associated with progressive disorientation. The electroencephalogram concurrently demonstrated prolonged spike-wave discharges, along with disturbance of background activity. Discontinuation of valproic acid resulted in immediate cessation of the prolonged and repetitive clusters of absence episodes and disappearance of drop attacks, along with sensorium clearing. In conclusion, although uncommon, a possible induction of absence status and even atonic seizures by valproic acid should be taken into account and properly managed by abrupt discontinuation of the drug.
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Affiliation(s)
- Eli Shahar
- Child Neurology Unit & Epilepsy Service, Rambam Medical Center, Rappaport School of Medicine, Haifa, Israel
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Otoom SA, Alkadhi KA. Epileptiform activity of veratridine model in rat brain slices: effects of antiepileptic drugs. Epilepsy Res 2000; 38:161-70. [PMID: 10642044 DOI: 10.1016/s0920-1211(99)00084-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effects of the antiepileptic drugs valproic acid (VPA), phenytoin (PHT), and ethosuximide (ESM) on evoked and spontaneous seizure-like (epileptiform) activity were studied in the veratridine epileptiform model in rat brain slices, using conventional electrophysiological intracellular recording techniques. The veratridine model is generated by treatment of brain slices with a low concentration (0.3 microM) of the alkaloid veratridine. The drug modifies sodium channel function so that a brief current injection in hippocampal CA1 pyramidal neurons evokes bursts of epileptiform activity. Therapeutic concentrations of VAP (50-200 microM) inhibited both evoked and spontaneous bursting in a voltage-dependent manner without affecting membrane resting potential or input resistance. Similarly, therapeutic concentrations of PHT (4-15 microM) inhibited both evoked and spontaneous bursting in a voltage-dependent fashion with no apparent change in the membrane resting potential. However, PHT increased the membrane input resistance and elevated the firing threshold of neurons. The antiepileptic drug ESM failed to inhibit evoked or spontaneous bursting even at high concentrations. The results suggest that the veratridine model of epileptiform activity is sensitive only to antiepileptic drugs that primarily affect the sodium channels.
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Affiliation(s)
- S A Otoom
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, TX 77204-5515, USA
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Otoom SA, Alkadhi KA. Valproic acid intensifies epileptiform activity in the hippocampal pyramidal neurons. Neurosci Res 1999; 35:299-307. [PMID: 10617321 DOI: 10.1016/s0168-0102(99)00099-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of large concentrations of valproic acid (VPA) on veratridine-induced epileptiform activity (veratridine model) were investigated in rat hippocampal CA1 pyramidal neurons. Studies were performed on the veratridine model in rat brain slices using conventional electrophysiological intracellular techniques. Large concentrations of VPA (5 mM or more) enhanced rather than inhibited epileptiform activity induced by veratridine. During the proepileptic phase of VPA, a membrane depolarization accompanied by a decrease in membrane input resistance were evident. The voltage-dependent proepileptic effect of VPA was blocked by tetrodotoxin (TTX; 100 nM) but not by the calcium channel blockers, diltiazem (5 microM) or omega-conotoxin GVIA (5 microM). VPA did not induce a proepileptic effect when it was superfused at high concentration (0.5-10 mM) on sodium channel-independent models such as the bicuculline or magnesium-free artificial cerebrospinal fluid. Large concentrations of VPA had no significant effect on untreated neurons. The VPA-enhanced veratridine bursting is probably related to the reported proepileptic activities observed in patients taking high doses of this drug. These data also suggest the involvement of sodium channels in the proepileptic effect of VPA.
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Affiliation(s)
- S A Otoom
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, TX 77204-5515, USA
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Abstract
Valproate is currently one of the major antiepileptic drugs with efficacy for the treatment of both generalized and partial seizures in adults and children. Furthermore, the drug is increasingly used for therapy of bipolar and schizoaffective disorders, neuropathic pain and for prophylactic treatment of migraine. These various therapeutic effects are reflected in preclinical models, including a variety of animal models of seizures or epilepsy. The incidence of toxicity associated with the clinical use of valproate is low, but two rare toxic effects, idiosyncratic fatal hepatotoxicity and teratogenicity, necessitate precautions in risk patient populations. Studies from animal models on structure-relationships indicate that the mechanisms leading to hepatotoxicity and teratogenicity are distinct and also differ from the mechanisms of anticonvulsant action of valproate. Because of its wide spectrum of anticonvulsant activity against different seizure types, it has repeatedly been suggested that valproate acts through a combination of several mechanisms. As shown in this review, there is substantial evidence that valproate increases GABA synthesis and release and thereby potentiates GABAergic functions in some specific brain regions, such as substantia nigra, thought to be involved in the control of seizure generation and propagation. Furthermore, valproate seems to reduce the release of the epileptogenic amino acid gamma-hydroxybutyric acid and to attenuate neuronal excitation induced by NMDA-type glutamate receptors. In addition to effects on amino acidergic neurotransmission, valproate exerts direct effects on excitable membranes, although the importance of this action is equivocal. Microdialysis data suggest that valproate alters dopaminergic and serotonergic functions. Valproate is metabolized to several pharmacologically active metabolites, but because of the low plasma and brain concentrations of these compounds it is not likely that they contribute significantly to the anticonvulsant and toxic effects of treatment with the parent drug. By the experimental observations summarized in this review, most clinical effects of valproate can be explained, although much remains to be learned at a number of different levels of valproate's mechanisms of action.
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Affiliation(s)
- W Löscher
- Department of Pharmacology, Toxicology and Pharmacy, School of Veterinary Medicine, Hannover, Germany.
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Albus H, Williamson R. Electrophysiologic analysis of the actions of valproate on pyramidal neurons in the rat hippocampal slice. Epilepsia 1998; 39:124-39. [PMID: 9577992 DOI: 10.1111/j.1528-1157.1998.tb01350.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE Studies in invertebrates and cultured mammalian neurons suggested that valproate (VPA) mediates its main antiepileptic effect by slowing the recovery from inactivation of voltage-dependent sodium channels. This predicts an effect on the refractory period of the action potential and, consequently, on the bursting behavior of neurons. METHODS We investigated this prediction using intracellular and extracellular recording techniques in hippocampal slices prepared from adult rats. The refractory period (RFP) and the ratio of the slopes (SR) of a pair of action potentials were used as indices of the recovery from inactivation of sodium channels. They were measured by injecting a series of paired depolarizing current pulses into CA1 pyramidal neurons. RESULTS No significant changes were observed in the RFP or SR measured during a 1-h recording period when VPA was bath-applied (1 mM), or when it was present in the recording electrode (10-50 mM). Lowering the temperature from 34.5 degrees C to 26.4 degrees C resulted in an increase of the RFP by 100% and a decrease of the SR by 40%. However, VPA did not affect any of the measured action potential parameters at this lower temperature. VPA was also without effect on the presynaptic fiber volley of axons recorded extracellularly in the stratum radiatum. The antidromic population spike was unaffected by VPA (2 mM), whereas phenytoin (50 microM) clearly affected this spike in the same slices. The absence of effect of VPA on each of the measured parameters could not be attributed to poor penetration through the slice because bath-applied VPA reduced the frequency of extracellularly recorded spontaneous interictal bursts, induced by bicuculline and elevated K+, within 10 min. CONCLUSIONS These findings suggest that at least in the hippocampal slice the drug's principal antiepileptic effect cannot be explained by its action on voltage-dependent sodium channels.
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Affiliation(s)
- H Albus
- Department of Physiology, Leiden University and the Instituut voor Epilepsiebestrijding, Heemstede, The Netherlands
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Tian LM, Alkadhi KA. Valproic acid inhibits the depolarizing rectification in neurons of rat amygdala. Neuropharmacology 1994; 33:1131-8. [PMID: 7862248 DOI: 10.1016/s0028-3908(05)80002-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The actions of valproic acid (VPA) on neuronal membrane properties and synaptic transmission were studied using intracellular recording techniques in rat basolateral neurons of the amygdala slices. In therapeutically attainable concentrations (10-100 microM), VPA decreased synaptically-induced epileptiform bursting in the presence of bicuculline. Additionally, the frequency of repetitive discharge induced by direct superthreshold depolarizing current pulses was decreased by VPA. However, evoked excitatory and inhibitory postsynaptic potentials were not affected at this level of drug concentration. The current-voltage relationship of untreated neurons revealed rectification of membrane potential when neuronal membrane was depolarized with cathodal current pulses. This depolarizing rectification was blocked by VPA. High medium calcium or addition of the sodium channel blocker tetrodotoxin (TTX) also blocked the depolarizing rectification, whereas the calcium channel antagonist diltiazem had no effect on the rectification. Elevation of medium calcium concentration also blocked the bicuculline-induced bursting. These results indicate that the inhibition by VPA of subthreshold slow sodium current and membrane depolarizing rectification results in suppression of neuronal membrane excitability which is probably a major mechanism for its anticonvulsant action.
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Affiliation(s)
- L M Tian
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, TX 77204-5515
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Gean PW, Huang CC, Hung CR, Tsai JJ. Valproic acid suppresses the synaptic response mediated by the NMDA receptors in rat amygdalar slices. Brain Res Bull 1994; 33:333-6. [PMID: 7904890 DOI: 10.1016/0361-9230(94)90202-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The mechanism of action of the anticonvulsant drug valproic acid (VPA) was studied in rat amygdaloid slices using intracellular recording techniques. In the presence of bicuculline (20 microM), stimulation of the endopyriform nucleus evoked an excitatory postsynaptic potential (EPSP) followed by a paroxysmal depolarizing shift (PDS). Superfusion of VPA (2 mM) reversibly suppressed the PDS. Synaptic response mediated by the N-methyl-D-aspartate (NMDA) receptors (EPSPNMDA) was isolated pharmacologically by application of a solution containing nonNMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and gamma-aminobutyric acid receptor antagonist bicuculline (20 microM). VPA (0.2-10 mM) reversibly reduced the amplitude of the EPSPNMDA in a dose-dependent manner. Higher concentration of VPA (10 mM), in addition, suppressed the normal synaptic transmission. These results suggest that VPA's anticonvulsant effect is due, at least in part, to its blocking action on the EPSPNMDA.
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Affiliation(s)
- P W Gean
- Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan, R.O.C
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Löscher W. Effects of the antiepileptic drug valproate on metabolism and function of inhibitory and excitatory amino acids in the brain. Neurochem Res 1993; 18:485-502. [PMID: 8097295 DOI: 10.1007/bf00967253] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Valproate is currently one of the major antiepileptic drugs in clinical use. Because of its wide spectrum of anticonvulsant activity against different seizure types, it has repeatedly been suggested that valproate acts through a combination of several mechanisms. As shown in this review, there is substantial evidence that valproate increases GABA turnover and thereby potentiates GABAergic functions in some specific brain regions, such as substantia nigra, thought to be involved in the control of seizure generation and propagation. Furthermore, valproate seems to reduce the release of the epileptogenic amino acid gamma-hydroxybutyric acid and to block cell firing induced by NMDA-type glutamate receptors. In addition to effects on amino acidergic neurotransmission, valproate presumably exerts a direct action on ion channels, thereby limiting sustained repetitive neuronal firing. Recent microdialysis data suggest that valproate also alters dopaminergic and serotonergic functions. These diverse effects of valproate might explain why the drug not only exerts anticonvulsant activity but also other pharmacodynamic and pharmacotherapeutic actions, such as antipsychotic and antidystonic efficacy.
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Affiliation(s)
- W Löscher
- Department of Pharmacology, School of Veterinary Medicine, Hannover, Germany
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Fueta Y, Avoli M. Effects of antiepileptic drugs on 4-aminopyridine-induced epileptiform activity in young and adult rat hippocampus. Epilepsy Res 1992; 12:207-15. [PMID: 1396546 DOI: 10.1016/0920-1211(92)90075-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Extracellular field potential recordings were used to study the effects of the antiepileptic drugs (AEDs) carbamazepine (CBZ), phenytoin (PHT), phenobarbital (PhB) and valproic acid (VPA) on the epileptiform activity evoked by 4-aminopyridine (4-AP, 50 microM) in the CA3 subfield of rat hippocampal slices obtained from young (8-23-day-old) and adult (> 60-day-old) male rats. Ictal (duration: 3-20 s; rate of occurrence: 3-12 x 10(-3) s-1) and interictal (duration: 0.2-0.8 s; rate of occurrence: 0.2-0.8 s-1) discharges were recorded in young slices, while only interictal activity (duration: 70-90 ms; rate of occurrence: 0.5-0.9 s-1) discharges were observed in adult slices. In addition, in both young and adult slices 4-AP disclosed a synchronous long-lasting potential (duration and rate of occurrence: 0.6-3 s, 7-70 x 10(-3) s-1 and 260-660 ms, 8-60 x 10(-3) s-1, respectively) that was caused by the activation of the gamma-aminobutyric acid type A (GABAA) receptor. In young slices, ictal discharges were blocked by CBZ (0.05 mM), PHT (0.1 mM), PhB (0.5 mM) and VPA (0.5 mM). With the exception of PhB, higher concentrations were necessary in these experiments for blocking the interictal activity (i.e., CBZ: 0.1 mM; PHT: > 0.2 mM; VPA: 2 mM). At these concentrations, none of the AEDs blocked the interictal activity in the adult hippocampus, but only reduced the rate of occurrence. PhB enhanced the rate of occurrence of the synchronous GABA-mediated long-lasting potentials both in young (increase: 190%) and in adult (increase: 145%) slices, while VPA increased their occurrence by 54% only in young slices. CBZ decreased the rate of occurrence of this long-lasting potential only in adult hippocampus. Our data indicate that the effects of the AEDs on 4-AP-induced epileptiform discharges are both pattern- and age-dependent. The rank order of potencies of the four AEDs was: (a) in young: CBZ > PHT > PhB > VPA; (b) in adult: CBZ > PhB > PHT > VPA.
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Affiliation(s)
- Y Fueta
- Montreal Neurological Institute, Que., Canada
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Zona C, Avoli M. Effects induced by the antiepileptic drug valproic acid upon the ionic currents recorded in rat neocortical neurons in cell culture. Exp Brain Res 1990; 81:313-7. [PMID: 2168843 DOI: 10.1007/bf00228121] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Rat neocortical neurons in culture were subjected to the whole cell mode of voltage clamping under experimental conditions designed to study Na+, Ca2+ and K+ currents in isolation. Following pharmacological blockade of most of the Ca2+ and K+ channels, depolarizing commands which brought the membrane potential from -80 to +10 mV elicited an inward current. This current was sensitive to tetrodotoxin (TTX) and was therefore caused by the opening of voltage-dependent channels permeable to Na+. Extracellular application of the antiepileptic drug valproic acid (VPA, 0.2-2mM) reduced in a dose-related, reversible way this Na+ current. VPA also evoked an increase of the voltage-dependent inward current recorded in the presence of TTX and thus presumably carried by Ca2+; this effect was seen in the presence of doses of VPA larger than 0.5 mM and was not reversible. Two types of outward K+ currents evoked by depolarizing steps in the presence of Na+ and Ca2+ channels blockers were not affected by VPA (up to 5 mM). Our data indicate that doses of VPA that are within the range present when it is used as an anticonvulsant, can influence inward currents generated by rat neocortical cells in culture. The reduction of the Na+, inward current is in line with findings obtained in mouse neurons by using standard intracellular recording techniques. This effect might represent an important mechanism of action for VPA in neocortex.
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Affiliation(s)
- C Zona
- Dipartimento di Medicina Sperimentale e Scienze Biochimiche, Università di Roma, Tor Vergata, Italy
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