[show abstract][hide abstract] ABSTRACT: Golgi cells (GoCs) are specialized interneurons that provide inhibitory input to granule cells in the cerebellar cortex. GoCs are pacemaker neurons that spontaneously fire action potentials, triggering spontaneous inhibitory postsynaptic currents in granule cells and also contributing to the generation tonic GABAA receptor-mediated currents in granule cells. In turn, granule cell axons provide feedback glutamatergic input to GoCs. It has been shown that high frequency stimulation of granule cell axons induces a transient pause in GoC firing in a type 2-metabotropic glutamate receptor (mGluR2)-dependent manner. Here, we investigated the effect ethanol on the pause of GoC firing induced by high frequency stimulation of granule cell axons. GoC electrophysiological recordings were performed in parasagittal cerebellar vermis slices from postnatal day 23 to 26 rats. Loose-patch cell-attached recordings revealed that ethanol (40 mM) reversibly decreases the pause duration. An antagonist of mGluR2 reduced the pause duration but did not affect the effect of ethanol. Whole-cell voltage-clamp recordings showed that currents evoked by an mGluR2 agonist were not significantly affected by ethanol. Perforated-patch experiments in which hyperpolarizing and depolarizing currents were injected into GoCs demonstrated that there is an inverse relationship between spontaneous firing and pause duration. Slight inhibition of the Na(+)/K(+) pump mimicked the effect of ethanol on pause duration. In conclusion, ethanol reduces the granule cell axon-mediated feedback mechanism by reducing the input responsiveness of GoCs. This would result in a transient increase of GABAA receptor-mediated inhibition of granule cells, limiting information flow at the input stage of the cerebellar cortex.
Frontiers in Integrative Neuroscience 01/2014; 8:10.
[show abstract][hide abstract] ABSTRACT: Exposure to ethanol (EtOH) during fetal development can lead to long-lasting alterations, including deficits in fine motor skills and motor learning. Studies suggest that these are, in part, a consequence of cerebellar damage. Cerebellar granule neurons (CGNs) are the gateway of information into the cerebellar cortex. Functionally, CGNs are heavily regulated by phasic and tonic GABAergic inhibition from Golgi cell interneurons; however, the effect of EtOH exposure on the development of GABAergic transmission in immature CGNs has not been investigated. To model EtOH exposure during the 3(rd) trimester-equivalent of human pregnancy, neonatal pups were exposed intermittently to high levels of vaporized EtOH from postnatal day (P) 2 to P12. This exposure gradually increased pup serum EtOH concentrations (SECs) to ∼60 mM (∼0.28 g/dl) during the 4 hours of exposure. EtOH levels gradually decreased to baseline 8 hrs after the end of exposure. Surprisingly, basal tonic and phasic GABAergic currents in CGNs were not significantly affected by postnatal alcohol exposure (PAE). However, PAE increased the expression of δ subunit expression at P28 as detected by immunohistochemical and western blot analyses. Also, electrophysiological studies with an agonist that is highly selective for δ-containing GABAA receptors, 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-3-ol (THIP), showed an increase in THIP-induced tonic current. Behavioral studies of PAE rats did not reveal any deficits in motor coordination, except for a delay in the acquisition of the mid-air righting reflex that was apparent at P15 to P18. These findings demonstrate that repeated intermittent exposure to high levels of EtOH during the equivalent of the last trimester of human pregnancy has significant but relatively subtle effects on motor coordination and GABAergic transmission in CGNs in rats.
[show abstract][hide abstract] ABSTRACT: Voltage-gated calcium channels (VGCCs) play a major role during the development of the central nervous system (CNS). Ca2+ influx via VGCCs regulates axonal growth and neuronal migration as well as synaptic plasticity. Specifically, L-type VGCCs have been well characterized to be involved in the formation and refinement of the connections within the CA3 region of the hippocampus. The majority of the growth, formation, and refinement in the CNS occurs during the third human trimester. An equivalent developmental time period in rodents occurs during the first 2weeks of post-natal life, and the expression pattern of L-type VGCCs during this time period has not been well characterized. In this study, we show that Cav1.2 channels are more highly expressed during this developmental period compared to adolescence (post-natal day 30) and that L-type VGCCs significantly contribute to the overall Ca2+ currents. These findings suggest that L-type VGCCs are functionally expressed during the crucial developmental period.
[show abstract][hide abstract] ABSTRACT: Although it is well documented that heavy consumption of alcohol during pregnancy impairs brain development, it remains controversial whether moderate consumption causes significant damage. Using a limited access, voluntary consumption paradigm, we recently demonstrated that moderate prenatal alcohol exposure (MPAE) is associated with dentate gyrus-dependent learning and memory deficits that are manifested in adulthood. Here, we identified a novel mechanism that may underlie this effect of MPAE. We found that MPAE mice exhibit deficits in NMDA receptor (NMDAR)-dependent long-term potentiation (LTP) in the dentate gyrus. Further, using semiquantitative immunoblotting techniques, we found that the levels of GluN2B subunits were decreased in the synaptic membrane, while levels of C2'-containing GluN1 and GluN3A subunits were increased, in the dentate gyrus of MPAE mice. These data suggest that MPAE alters the subunit composition of synaptic NMDARs, leading to impaired NMDAR-dependent LTP in the dentate gyrus.
Journal of Neuroscience 01/2013; 33(3):1062-7. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cerebellar granule cells (CGNs) are one of many neurons that express phasic and tonic GABAergic conductances. Although it is well established that Golgi cells (GoCs) mediate phasic GABAergic currents in CGNs, their role in mediating tonic currents in CGNs (CGN-I(tonic)) is controversial. Earlier studies suggested that GoCs mediate a component of CGN-I(tonic) that is present only in preparations from immature rodents. However, more recent studies have detected a GoC-dependent component of CGN-I(tonic) in preparations of mature rodents. In addition, acute exposure to ethanol was shown to potentiate the GoC component of CGN-I(tonic) and to induce a parallel increase in spontaneous inhibitory postsynaptic current frequency at CGNs. Here, we tested the hypothesis that these effects of ethanol on GABAergic transmission in CGNs are mediated by inhibition of the Na(+)/K(+)-ATPase. We used whole-cell patch-clamp electrophysiology techniques in cerebellar slices of male rats (postnatal day 23-30). Under these conditions, we reliably detected a GoC-dependent component of CGN-I(tonic) that could be blocked with tetrodotoxin. Further analysis revealed a positive correlation between basal sIPSC frequency and the magnitude of the GoC-dependent component of CGN-I(tonic). Inhibition of the Na(+)/K(+)-ATPase with a submaximal concentration of ouabain partially mimicked the ethanol-induced potentiation of both phasic and tonic GABAergic currents in CGNs. Modeling studies suggest that selective inhibition of the Na(+)/K(+)-ATPase in GoCs can, in part, explain these effects of ethanol. These findings establish a novel mechanism of action of ethanol on GABAergic transmission in the central nervous system.
PLoS ONE 01/2013; 8(1):e55673. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Fetal alcohol spectrum disorders are often associated with structural and functional hippocampal abnormalities, leading to long-lasting learning and memory deficits. The mechanisms underlying these abnormalities are not fully understood. Here, we investigated whether ethanol exposure during the 3rd trimester-equivalent period alters spontaneous network activity that is involved in neuronal circuit development in the CA3 hippocampal region. This activity is driven by GABA(A) receptors, which can have excitatory actions in developing neurons as a consequence of greater expression of the Cl(-) importer, NKCC1, with respect to expression of the Cl(-) exporter, KCC2, resulting in high [Cl(-)](i). Rat pups were exposed to ethanol vapor from postnatal day (P) 2-16 (4 h/day). Weight gain was significantly reduced in pups exposed to ethanol compared to control at P15 and 16. Brain slices were prepared immediately after the end of the 4-h exposure on P4-16 and experiments were also performed under ethanol-free conditions at the end of the exposure paradigm (P17-22). Ethanol exposure did not significantly affect expression of KCC2 or NKCC1, nor did it affect network activity in the CA3 hippocampal region. Ethanol exposure significantly decreased the frequency (at P9-11) and increased the amplitude (at P5-8 and P17-21) of GABA(A) receptor-mediated miniature postsynaptic currents. These data suggest that repeated in vivo exposure to ethanol during the 3rd trimester-equivalent period alters GABAergic transmission in the CA3 hippocampal region, an effect that could lead to abnormal circuit maturation and perhaps contribute to the pathophysiology of fetal alcohol spectrum disorders.
[show abstract][hide abstract] ABSTRACT: Although public health campaigns advise pregnant women to abstain from ethanol, drinking during pregnancy is pervasive. Here, we highlight recent studies that have clearly demonstrated long-lasting neurobehavioral deficits in the offspring of laboratory animals exposed to moderate levels of ethanol during development. Alterations in learning, memory, motor coordination, social behavior, and stress responses were identified in these animals. Increased vulnerability to substance abuse was also demonstrated. These behavioral alterations have been associated with impairments in neurotransmitter systems, neuromodulators, and/or synaptic plasticity in several brain regions. With this review we hope to contribute to a better appreciation of the potential effects of developmental exposure to moderate ethanol levels, leading to better interventions aimed at relieving fetal alcohol spectrum disorders.
Trends in Neurosciences 03/2012; 35(5):284-92. · 13.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: This study assessed the acute effect of ethanol on GABAergic transmission at molecular layer interneurons (MLIs; i.e. basket and stellate cells) in the cerebellar cortex. The actions of ethanol on spontaneous firing of these pacemaker neurons were also measured.
Transgenic mice (glutamic acid-decarboxylase 67-green fluorescent protein knock-in mice) that express green fluorescence protein in GABAergic interneurons were used to aid in the identification of MLIs. Parasagittal cerebellar slices were prepared and whole-cell patch-clamp electrophysiological techniques were used to measure GABA(A) receptor-mediated spontaneous and miniature inhibitory postsynaptic currents (sIPSCs and mIPSCs). Loose-seal cell-attached recordings were used to measure spontaneous action potential firing.
Stellate cells received spontaneous GABAergic input in the form of a mixture of action potential-dependent events (sIPSCs) and quantal events (mIPSCs); ethanol increased sIPSC frequency to a greater extent than mIPSC frequency. Ethanol increased spontaneous action potential firing of MLIs, which could explain the increase in sIPSC frequency in stellate cells. Basket cells received GABAergic input in the form of quantal events only. Ethanol significantly increased the frequency of these events, which may be mediated by a different type of interneuron (perhaps, the Lugaro cell) or Purkinje cell collaterals.
Ethanol exposure differentially increases GABA release at stellate cell vs. basket cell-to-Purkinje cell synapses. This effect may contribute to the abnormalities in cerebellar function associated with alcohol intoxication.
Alcohol and Alcoholism 11/2011; 47(1):1-8. · 1.96 Impact Factor
[show abstract][hide abstract] ABSTRACT: Studies with rodents suggest that acute ethanol exposure impairs information flow through the cerebellar cortex, in part, by increasing GABAergic input to granule cells. Experiments suggest that an increase in the excitability of specialized GABAergic interneurons that regulate granule cell activity (i.e., Golgi cells [GoCs]) contributes to this effect. In GoCs, ethanol increases spontaneous action potential firing frequency, decreases the afterhyperpolarization amplitude, and depolarizes the membrane potential. Studies suggest that these effects could be mediated by inhibition of the Na(+)/K(+) ATPase. The purpose of this study was to characterize the potential role of other GoC conductances in the mechanism of action of ethanol.
Computer modeling techniques and patch-clamp electrophysiological recordings with acute slices from rat cerebella were used for these studies.
Computer modeling suggested that modulation of subthreshold Na(+) channels, hyperpolarization-activated currents, and several K(+) conductances could explain some but not all actions of ethanol on GoCs. Electrophysiological studies did not find evidence consistent with a contribution of these conductances. Quinidine, a nonselective blocker of several types of channels (including several K(+) channels) that also antagonizes the Na(+)/K(+) ATPase, reduced the effect of ethanol on GoC firing.
These findings further support that ethanol increases GoC excitability via modulation of the Na(+)/K(+) ATPase and suggest that a quinidine-sensitive K(+) channel may also play a role in the mechanism of action of ethanol.
Alcoholism Clinical and Experimental Research 10/2011; 36(4):616-24. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: The functional implications of transient receptor potential melastatin 3 (TRPM3) activation, the most recently described member of the melastatin subfamily of cation permeable TRP channels, have begun to be elucidated in recent years. The discovery of TRPM3 activation by the steroid pregnenolone sulfate (PregS) has shed new light on the physiological role of this channel. For example, TRPM3 activation enhances insulin secretion from β pancreatic cells, induces contraction of vascular smooth muscle, and is also involved in the detection of noxious heat. Although TRPM3 expression has been detected in several regions of the developing and mature brain, little is known about the roles of TRPM3 in brain physiology. In this study, we demonstrate the abundant expression of TRPM3 steroid-sensitive channels in the developing cerebellar cortex. We also show that TRPM3-like channels are expressed at glutamatergic synapses in neonatal Purkinje cells. We recently showed that PregS potentiates spontaneous glutamate release onto neonatal Purkinje cells during a period of active glutamatergic synapse formation; we now show that this effect of PregS is mediated by TRPM3-like channels. Mefenamic acid, a recently discovered TRPM3 antagonist, blocked the effect of PregS on glutamate release. The PregS effect on glutamate release was mimicked by other TRPM3 agonists (nifedipine and epipregnanolone sulfate) but not by a TRMP3-inactive steroid (progesterone). Our findings identify TRPM3 channels as novel modulators of glutamatergic transmission in the developing brain.
Journal of Neurochemistry 08/2011; 119(3):474-85. · 3.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: The adolescent brain is particularly vulnerable to the effects of alcohol, with intoxications at this developmental age often producing long-lasting effects. The present study addresses the effects of a single acute ethanol exposure on growth-associated protein-43 (GAP-43) and brain-derived neurotrophic factor (BDNF) gene expression in neurons in the cerebellum and hippocampus of adolescent rats. Male postnatal day 23 (P23) Sprague-Dawley rats were exposed to ethanol vapors for 2h and after a recovery period of 2h, the cerebellum and hippocampus were harvested and samples were taken for blood alcohol concentration (BAC) determinations. We found that this exposure resulted in a mean BAC of 174 mg/dL, which resembles levels in human adolescents after binge drinking. Analyses of total RNA and protein by quantitative reverse transcription PCR and western blotting, respectively, revealed that this single ethanol exposure significantly decreased the levels of GAP-43 mRNA and protein in the cerebellum but increased the levels of mRNA and protein in the hippocampus. BDNF mRNA and protein levels were also increased in the hippocampus but not in the cerebellum of these animals. In situ hybridizations revealed that GAP-43 and BDNF mRNA levels were primarily increased by alcohol exposure in hippocampal dentate granule cells and CA3 neurons. Overall, the reported alterations in the expression of the plasticity-associated genes GAP-43 and BDNF in juvenile rats are consistent with the known deleterious effects of binge drinking on motor coordination and cognitive function.
[show abstract][hide abstract] ABSTRACT: Development of cerebellar Purkinje cells (PCs) is modulated by neuroactive steroids. Developing hippocampal pyramidal neurons retrogradely release a pregnenolone sulfate (PregS)-like neurosteroid that may contribute to glutamatergic synapse stabilization. We hypothesized that PregS could exert a similar effect on developing PCs. To test this hypothesis, we performed whole-cell patch-clamp recordings from PCs in acute cerebellar vermis slices from neonatal rats. PregS induced a robust (∼3000%) and reversible increase in AMPA receptor-mediated miniature excitatory postsynaptic current (AMPA-mEPSC) frequency without affecting the amplitude, time-to-rise, or half-width of these events. PregS also increased the frequency of GABA(A) receptor-mediated miniature postsynaptic currents but to a significantly lesser extent (<100%). The PregS-induced increase of AMPA-mEPSC frequency was not significantly decreased by antagonists of receptors (NMDA, glycine, α7 nicotinic acetylcholine and σ1) that have been shown to modulate glutamatergic transmission at PCs and/or mediate the actions of PregS on neurotransmitter release. Ca(2+) chelation experiments suggested that PregS acts by increasing presynaptic terminal [Ca(2+)](i), an effect that is independent of voltage-gated Ca(2+) channels, but is blocked by the antagonist of transient receptor potential (TRP) channels, La(3+). PregS also increased the amplitude of EPSCs evoked by climbing fiber (CF) stimulation and decreased the paired-pulse ratio of these events. Neither CF nor parallel fiber-evoked EPSCs were affected by PregS in slices from juvenile rats. These results suggest that glutamate release at CF-to-PC synapses is an important target of PregS in the neonatal cerebellar cortex, an effect that may play a role in the refinement of these synapses.
[show abstract][hide abstract] ABSTRACT: Fetal alcohol exposure affects 1 in 100 children making it the leading cause of mental retardation in the US. It has long been known that alcohol affects cerebellum development and function. However, the underlying molecular mechanism is unclear.
We demonstrate that CREB binding protein (CBP) is widely expressed in granule and Purkinje neurons of the developing cerebellar cortex of naïve rats. We also show that exposure to ethanol during the 3(rd) trimester-equivalent of human pregnancy reduces CBP levels. CBP is a histone acetyltransferase, a component of the epigenetic mechanism controlling neuronal gene expression. We further demonstrate that the acetylation of both histone H3 and H4 is reduced in the cerebellum of ethanol-treated rats.
These findings indicate that ethanol exposure decreases the expression and function of CBP in the developing cerebellum. This effect of ethanol may be responsible for the motor coordination deficits that characterize fetal alcohol spectrum disorders.
PLoS ONE 01/2011; 6(5):e19351. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Neurotransmitter systems have been long recognized as important targets of the developmental actions of alcohol (i.e., ethanol). Short- and long-term effects of ethanol on amino acid (e.g.,-aminobutyric acid and glutamate) and biogenic amine (e.g., serotonin and dopamine) neurotransmitters have been demonstrated in animal models of fetal alcohol spectrum disorders (FASD). Researchers have detected ethanol effects after exposure during developmental periods equivalent to the first, second, and third trimesters of human pregnancy. Results support the recommendation that pregnant women should abstain from drinking-even small quantities-as effects of ethanol on neurotransmitter systems have been detected at low levels of exposure. Recent studies have elucidated new mechanisms and/or consequences of the actions of ethanol on amino acid and biogenic amine neuro-transmitter systems. Alterations in these neurotransmitter systems could, in part, be responsible for many of the conditions associated with FASD, including (1) learning, memory, and attention deficits; (2) motor coordination impairments; (3) abnormal responsiveness to stress; and (4) increased susceptibility to neuropsychiatric disorders, such as substance abuse and depression, and also neurological disorders, such as epilepsy and sudden infant death syndrome. However, future research is needed to conclusively establish a causal relationship between these conditions and developmental dysfunctions in neurotransmitter systems.
Alcohol research & health: the journal of the National Institute on Alcohol Abuse and Alcoholism 01/2011; 34(1):106-20. · 0.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: The granule cell layer of the cerebellum functions in spatio-temporal encoding of information. Granule cells (GCs) are tonically inhibited by spillover of GABA released from Golgi cells and this tonic inhibition is facilitated by acute ethanol. Recently, it was demonstrated that a specialized Ca(2+)-activated anion-channel, bestrophin1 (Best1), found on glial cells, can release GABA that contributes up to 50-75% of the tonic GABAergic current. However, it is unknown if ethanol has any actions on Best1 function. Using whole-cell electrophysiology, we found that recombinant Best1 channels expressed in HEK-293 cells were insensitive to 40 and 80 mM ethanol. We attempted to measure the Best1-mediated component of the tonic current in slices using 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). We confirmed that this agent blocks recombinant Best1 channels. Unexpectedly, we found that NPPB significantly potentiated the tonic current and the area and decay of GABA(A)-mediated spontaneous inhibitory post-synaptic currents (IPSCs) in GCs in rodent slices under two different recording conditions. To better isolate the Best1-dependent tonic current component, we blocked the Golgi cell component of the tonic current with tetrodotoxin and found that NPPB similarly and significantly potentiated the tonic current amplitude and decay time of miniature IPSCs. Two other Cl(-)-channel blockers were also tested: 4'-diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate (DIDS) showed no effect on GABAergic transmission, while niflumic acid (NFA) significantly suppressed the tonic current noise, as well as the mIPSC frequency, amplitude, and area. These data suggest that acute ethanol exposure does not modulate Best1 channels and these findings serve to challenge recent data indicating that these channels participate in the generation of tonic GABAergic currents in cerebellar GCs.
[show abstract][hide abstract] ABSTRACT: Recent findings from our laboratory indicate that alterations in frontal cortex function, structural plasticity, and related social behaviors are persistent consequences of exposure to moderate levels of ethanol during prenatal brain development . Fetal-ethanol-related reductions in the expression of the immediate early genes (IEGs) c-fos and Arc and alterations in dendritic spine density in ventrolateral and medial aspects of frontal cortex suggest a dissociation reminiscent of that described by Kolb et al.  in which these aspects of frontal cortex undergo reciprocal experience-dependent changes. In addition to providing a brief review of the available data on social behavior and frontal cortex function in fetal-ethanol-exposed rats, the present paper presents novel data on social-experience-related IEG expression in four regions of frontal cortex (Zilles LO, VLO, Fr1, Fr2) that are evaluated alongside our prior data from AID and Cg3. Social experience in normal rats was related to a distinct pattern of IEG expression in ventrolateral and medial aspects of frontal cortex, with generally greater expression observed in ventrolateral frontal cortex. In contrast, weaker expression was observed in all aspects of frontal cortex in ethanol-exposed rats, with the exception of an experience-related increase in the medial agranular cortex. Behaviors related to social investigation and wrestling/boxing were differentially correlated with patterns of activity-related IEG expression in the regions under investigation for saccharin- and ethanol-exposed rats. These observations suggest that recruitment and expression of IEGs in frontal cortex following social experience are potentially important for understanding the long-term consequences of moderate prenatal ethanol exposure on frontal cortex function, synaptic plasticity, and related behaviors.
Behavioural brain research 12/2010; 214(1):66-74. · 3.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: Adolescent rats are less sensitive to the motor-impairing effects of ethanol than adults. However, the cellular and molecular mechanisms underlying this age-dependent effect of ethanol have yet to be fully elucidated.
Male rats of various ages were used to investigate ethanol-induced ataxia and its underlying cellular correlates. In addition, Purkinje neurons from adolescent and adult rats were recorded both in vivo and in vitro. Finally, protein kinase C (PKCγ) expression was determined in 3 brain regions in both adolescent and adult rats.
The present multi-methodological investigation confirms that adolescents are less sensitive to the motor-impairing effects of ethanol, and this differential effect is not because of differential blood ethanol levels. In addition, we identify a particular cellular correlate that may underlie the reduced motor impairment. Specifically, the in vivo firing rate of cerebellar Purkinje neurons recorded from adolescent rats was insensitive to an acute ethanol challenge, while the firing rate of adult cerebellar Purkinje neurons was significantly depressed. Finally, it is demonstrated that PKCγ expression in the cortex and cerebellum mirrors the age-dependent effect of ethanol: adolescents have significantly less PKCγ expression compared to adults.
Adolescents are less sensitive than adults to the motor-impairing effects of ethanol, and a similar effect is seen with in vivo electrophysiological recordings of cerebellar Purkinje neurons. While still under investigation, PKCγ expression mirrors the age effect of ethanol and may contribute to the age-dependent differences in the ataxic effects of ethanol.
Alcoholism Clinical and Experimental Research 12/2010; 34(12):2070-80. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Alcohol-induced alterations of cerebellar function cause motor coordination impairments that are responsible for millions of injuries and deaths worldwide. Cognitive deficits associated with alcoholism are also a consequence of cerebellar dysfunction. The mechanisms responsible for these effects of ethanol are poorly understood. Recent studies have identified neurons in the input layer of the cerebellar cortex as important ethanol targets. In this layer, granule cells (GrCs) receive the majority of sensory inputs to the cerebellum through the mossy fibers. Information flow at these neurons is gated by a specialized pacemaker interneuron known as the Golgi cell, which provides divergent GABAergic input to thousands of GrCs. In vivo electrophysiological experiments have previously shown that acute ethanol exposure abolishes GrC responsiveness to sensory inputs carried by mossy fibers. Slice electrophysiological studies suggest that ethanol causes this effect by potentiating GABAergic transmission at Golgi cell-to-GrC synapses through an increase in Golgi cell excitability. Using patch-clamp electrophysiological techniques in cerebellar slices and computer modeling, we show here that ethanol excites Golgi cells by inhibiting the Na(+)/K(+) ATPase. Voltage-clamp recordings of Na(+)/K(+) ATPase currents indicated that ethanol partially inhibits this pump and this effect could be mimicked by low concentrations of ouabain. Partial inhibition of Na(+)/K(+) ATPase function in a computer model of the Golgi cell reproduced these experimental findings. These results establish a novel mechanism of action of ethanol on neuronal excitability, which likely has a role in ethanol-induced cerebellar dysfunction and may also contribute to neuronal functional alterations in other brain regions.
Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 08/2010; 35(9):1984-96. · 6.99 Impact Factor
[show abstract][hide abstract] ABSTRACT: Fetal alcohol spectrum disorder (FASD) is associated with learning and memory alterations that could be, in part, a consequence of hippocampal damage. The CA3 hippocampal subfield is one of the regions affected by ethanol (EtOH), including exposure during the third trimester-equivalent (i.e., neonatal period in rats). However, the mechanism of action of EtOH is poorly understood. In CA3 pyramidal neurons from neonatal rats, dendritic BDNF release causes long-term potentiation of the frequency of GABAA receptor-mediated spontaneous postsynaptic currents (LTP-GABAA) and this mechanism is thought to play a role in GABAergic synapse maturation. Here, we show that short- and long-term exposure of neonatal male rats to low EtOH concentrations abolishes LTP-GABAA by inhibiting L-type voltage-gated Ca2+ channels. These findings support the recommendation that even light drinking should be avoided during pregnancy.
Journal of Neuroscience 05/2010; 30(19):6776-81. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Developmental ethanol exposure damages the hippocampus, causing long-lasting learning and memory deficits. Synaptic plasticity mechanisms (e.g., long-term potentiation [LTP]) contribute to synapse formation and refinement during development. We recently showed that acute ethanol exposure inhibits glutamatergic synaptic transmission and N-methyl-d-aspartate receptor (NMDAR)-dependent LTP in the CA1 hippocampal region of postnatal day (P)7-9 rats. The objective of this study was to further characterize the effect of ethanol on LTP in the developing CA1 hippocampus during the third trimester equivalent. To more closely model human ethanol exposure during this period, rat pups were exposed to ethanol vapor (2 or 4.5 g/dL in air, serum ethanol concentrations=96.6-147.2 or 322-395.6 mg/dL) from P2-9 (4h/d). Brain slices were prepared immediately after the end of the 4-h exposure on P7-9 and extracellular electrophysiological recordings were performed 1-7h later under ethanol-free conditions to model early withdrawal. LTP was not different than group-matched controls in the 96.6-147.2mg/dL group; however, it was impaired in the 322-395.6 mg/dL group. Neither alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (AMPAR)/NMDAR function nor glutamate release were affected in the 322-395.6 mg/dL ethanol exposure group. These data suggest that repeated in vivo exposure to elevated ethanol doses during the third trimester-equivalent period impairs synaptic plasticity, which may alter maturation of hippocampal circuits and ultimately contribute to the long-lasting cognitive deficits associated with fetal alcohol spectrum disorders.