Brain plasticity and cognitive functions after ethanol consumption in C57BL/6J mice.

Acute or chronic administrations of high doses of ethanol in mice are known to produce severe cognitive deficits linked to hippocampal damage. However, we recently reported that chronic and moderate ethanol intake in C57BL/6J mice induced chromatin remodeling within the Bdnf promoters, leading to both enhanced brain-derived neurotrophic factor (BDNF) expression and hippocampal neurogenesis under free-choice protocol. We performed here a series of cellular and behavioral studies to analyze the consequences of these modifications. We showed that a 3-week chronic free-choice ethanol consumption in C57BL/6J mice led to a decrease in DNA methylation of the Bdnf gene within the CA1 and CA3 subfields of the hippocampus, and upregulated hippocampal BDNF signaling pathways mediated by ERK, AKT and CREB. However, this activation did not affect long-term potentiation in the CA1. Conversely, ethanol intake impaired learning and memory capacities analyzed in the contextual fear conditioning test and the novel object recognition task. In addition, ethanol increased behavioral perseveration in the Barnes maze test but did not alter the mouse overall spatial capacities. These data suggested that in conditions of chronic and moderate ethanol intake, the chromatin remodeling leading to BDNF signaling upregulation is probably an adaptive process, engaged via epigenetic regulations, to counteract the cognitive deficits induced by ethanol.

Web-based tool for injury risk assessment of foreign body injuries in children.

Web-based surveillance systems enhance the ability for identifying, estimating and assessing public health hazards. In this paper we describe the development of a Web-based surveillance registry called Susy Safe for inorganic foreign body injuries in children aged 0-14. The Susy Safe system, which collected 2103 cases during 2000-2002 in 19 European countries, allows for notifying from physicians over the internet thus taking advantage of Web reporting capabilities. Functions include automated risk analysis engine and results visualization. Risk analysis engine has been implemented in a Bayesian framework and provides an update estimate of the risk profile of the products causing injuries, effectively as new data become available. The system contributes to simplify the physician reporting and improve public health information dissemination within consumers and consumers' association. Also it gives physician and researcher the access of a large amount of data otherwise scattered all around in different hospitals. Finally, supplying a quantitative risk assessment for the identification of hazardous characteristics of objects, such as dimensions or shape, it works toward an improvement of consumer products' safety design.

Are FPCIs a source of increased risk for children? Results of a multicenter, experimental study comparing children's behaviour with FPCIs and toys.

INTRODUCTION: Food Products Containing Inedibles (FPCIs) are believed to represent a source of higher choking risk in children. The aim of this study was to set up a controlled study, conducted on children aged 3-6 in a laboratory setting, in order to understand their behavior when interacting with FPCIs (with reference to mouthing activities, double nature recognition, and toy assembling ability). METHOD: The experimental phase was divided into two sessions: a FPCI session and a Toy session, to which 247 children were randomly assigned. During these sessions children were observed in order to catch their mouthing activity according to the two types of objects available to them (FPCIs and Toys). RESULTS: This study shows that: (a) children's behavior with respect to toys contained in FPCIs and toys presented alone is not significantly different; (b) children's ability to distinguish between the edible and non-edible part of the FPCI was very high; and (c) mouthing episodes of the inedible parts were negligible and comparable between FPCIs and toys presented alone. This strongly suggests that, with respect to choking risk, FPCIs are not per se distinguishable from toys containing small parts. IMPACT ON INDUSTRY: Restrictions on the sale of FPCIs with small toys exist in the U.S. market. In Europe, FPCIs are allowed to be on sale, under the condition that, in case, they will follow the general regulatory requirements of small toys packaged and sold alone. In this case, they must provide age warnings and labels. Our findings do not justify the different attention that toys in FPCIs are at times afforded by regulators when compared to "stand alone" toys.

The cost of foreign body injuries in the upper aero-digestive tract: need for a change from a clinical to a public health perspective?

OBJECTIVE: This paper addressed the impact in terms of direct costs of the injuries in children due to foreign bodies in the upper aero-digestive tract. METHODS: Two thousand one hundred and three consecutive cases were collected from 2000 to 2002 in 16 European hospitals, 1 hospital for each participating country, and referred to children aged until 14 who had FB injuries. Costs were based on the extraction of the FB procedures and on hospitalization length, based on DRGs. Determinants of costs and of length of stay (LOS) were analyzed using a multilevel model. RESULTS: The major cost of the treatment of FB injuries is covered by the ENT Departments, which are usually the first choice of referral, directly from the patients. Children had a mean LOS of 2.13 days (95% C.I. 1.99-2.29). Treatment of the FB was associated with a mean cost of euro 1017.37 (95% C.I. 963.27-1073.51). In the multivariable analysis higher costs are related to the modality of arrival to the hospital by walk, to the site of the injury (ICD-933, ICD-934, ICD-935 in particular) and to the use of surgery in removing the FB. DISCUSSION: Foreign bodies injuries are posing a great threat not only with regards to the clinical aspects but also from the public health perspective, their treatment being associated with high costs, in particular when surgery is needed.

Foreign bodies in the upper airways: the experience of two Italian hospitals.

OBJECTIVE: To study the pattern of foreign bodies in the upper airways as emerging from the hospital records in the Bologna and Siena hospitals in Italy 1997-2002. METHODS: A retrospective review of hospital records was performed using a standardized protocol. All injuries with ICD9 (International Classification of Diseases, 9'h revision) codes ranging from 931 to 934 which occurred in children age 0-14 were considered for the database. RESULTS: One hundred ninety seven patients were included in the database with a diagnosis of Foreign Bodies (FB) over the study period, 78 with ICD931, 105 with ICD932, 12 with ICD933 and 2 with ICD934 discharge diagnosis. Of the 197 patients, 51.90% of the patients were males and the 48.10% were female. Median age was 4 (2, 6). At the moment of the injury, the child was eating (11%), playing (83%) or studying (4%) or cleaning ears (2%). The child was supervised by an adult in doing his/her activities at the moment of injury in the 84.2% of the cases. The child reached the hospital using always private transport (100%), never by using an emergency transport (0%). Most commonly, FB were extracted in ambulatory (95.4%), more rarely using an endoscopic procedure (4.1%), and never using surgery. Hospitalization was required in the 0.5% of cases (1). CONCLUSIONS: Our study showed the substantial epidemiological similarity of the Italian data with the experience of other center in the world. The burden of chocking was very limited in our country, as proven by the limited access to emergency and more invasive procedures. Nevertheless, some consideration can be made from the preventive point of view. Quite surprisingly, the majority of injuries occurred under the supervision of an adult in playing or recreational activities.

Child mortality due to suffocation in Europe (1980-1995): a review of official data.

This report outlines the current status of the official statistical data available concerning mortality rates for suffocation in children <15 years of age, stratified according to sex and country in Europe, in the years 1980-1995. The data source is the WHO Mortality Database, which comprises deaths registered in national vital registration systems, with underlying cause of death as coded by the relevant national authority. To assess the impact of the problem of suffocation, the total potential years of life lost have been calculated. In addition, for Italy, and for the years 1999-2000, data related to deaths and hospitalizations for foreign body in the pharynx and larynx are presented. In Italy, in the years 1999-2000, the ratio between the number of hospitalizations and the mortality rates is approximately one death every 10 hospitalizations (x 100,000). The European mortality rate exceeds nearly one death per 100,000 persons. No evidence of any geographical pattern or cyclic trend emerged from the analysis of this official data.

Psychological aspects of risk appraisal in asphyxiation accidents: a review of the factors influencing children's perception and behaviour.

Psychological aspects determining children's behaviour in response to asphyxiation risk due to ingestion of foreign matter have been rarely and non-systematically examined in the literature. Aim of this report is to highlight--through a review of the most significant psychological research in the literature--which factors influence the behaviour, perception and assessments of children 0 to 14 years of age, in a risk situation. In particular, attention is focused on the direct experience of a child at risk, assuming that this experience can play a significant role in future dangerous situations. Outcomes of studies taken into consideration have highlighted the influence of age, sex, socio-economic status, parents' role, peer group, personal traits, television and personal experience. The latter refutes the initial hypotheses, showing an unexpected and clearly negative effect on future evaluation and behaviour in response to similar contexts of asphyxiation risk. The implications for research on asphyxiation due to ingestion of foreign matter are examined.

Selective inhibition of local excitatory synaptic transmission by serotonin through an unconventional receptor in the CA1 region of rat hippocampus.

1. The modulation of synaptic transmission by serotonin (5-HT) was studied using whole-cell voltage-clamp and sharp-electrode current-clamp recordings from CA1 pyramidal neurones in transverse rat hippocampal slices in vitro. 2. With GABA(A) receptors blocked, polysynaptic transmission evoked by stratum radiatum stimulation was inhibited by submicromolar concentrations of 5-HT, while monosynaptic excitatory transmission and CA1 pyramidal neurone excitability were unaffected. The effect persisted following pharmacological blockade of 5-HT(1A) and 5-HT(4) receptors, which directly affect CA1 pyramidal neurone excitability. 3. Concentration-response relationships for 5-HT were determined in individual neurones; the EC(50) values for block of polysynaptic excitation and inhibition by 5-HT were approximately 230 and approximately 160 nM, respectively. The 5-HT receptor type responsible for the observed effect does not fall easily into the present classification of 5-HT receptors. 4. 5-HT inhibition of polysynaptic EPSCs persisted following complete block of GABAergic transmission and in CA1 minislices, ruling out indirect effects through interneurones and non-CA1 pyramidal neurones, respectively. 5. Monosynaptic EPSCs evoked by stimulation of CA1 afferent pathways appeared to be unaffected by 5-HT. Monosynaptic EPSCs evoked by stimulation of the alveus, which contains CA1 pyramidal neurone axons, were partially inhibited by 5-HT. 6. We conclude that 5-HT inhibited synaptic transmission by acting at local recurrent collaterals of CA1 pyramidal neurones. This may represent an important physiological action of 5-HT in the hippocampus, since it occurs over a lower concentration range than the 5-HT effects reported so far.

Effect of A2A adenosine receptor stimulation and antagonism on synaptic depression induced by in vitro ischaemia in rat hippocampal slices.

1. In the present study we investigated the role of A2A adenosine receptors in hippocampal synaptic transmission under in vitro ischaemia-like conditions. 2. The effects of adenosine, of the selective A2A receptor agonist, CGS 21680 (2-[p-(2-carboxyethyl)-phenethylamino]-5'-N-ethylcarboxamidoade nos ine ), and of selective A2A receptor antagonists, ZM 241385 (4-(2-[7-amino-2-(2-furyl)-¿1,2,4¿-triazolo¿2,3-a¿¿1,3, 5¿triazin-5-ylamino]ethyl)phenol) and SCH 58261 (7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2, 4-triazolo[1,5-c]pyrimidine), have been evaluated on the depression of field e.p.s.ps induced by an in vitro ischaemic episode. 3. The application of 2 min of in vitro ischaemia brought about a rapid and reversible depression of field e.p.s.ps, which was completely prevented in the presence of the A1 receptor antagonist DPCPX (1, 3-dipropyl-8-cyclopentylxanthine) (100 nM). On the other hand both A2A receptor antagonists, ZM 241385 and SCH 58261, by themselves did not modify the field e.p.s.ps depression induced by in vitro ischaemia. 4. A prolonged application of either adenosine (100 micronM) or CGS 21680 (30, 100 nM) before the in vitro ischaemic episode, significantly reduced the synaptic depression. These effects were antagonized in the presence of ZM 241385 (100 nM). 5. SCH 58261 (1 and 50 nM) did not antagonize the effect of 30 nM CGS 21680 on the ischaemia-induced depression. 6. These results indicate that in the CA1 area of the hippocampus the stimulation of A2A adenosine receptors attenuates the A1-mediated depression of synaptic transmission induced by in vitro ischaemia.

Biochemical and electrophysiological studies on (S)-(+)-2-(3'-carboxybicyclo(1.1.1)pentyl)-glycine (CBPG), a novel mGlu5 receptor agonist endowed with mGlu1 receptor antagonist activity.

The pharmacological profile of (S)-(+)-2-(3'-carboxybicyclo[1.1.1]pentyl)-glycine (CBPG) and of other group 1 metabotropic glutamate (mGlu) receptor agents were studied in BHK cells transfected with mGlu receptor subtypes or in native receptors in brain slices by measuring second messenger responses. The mGlu receptor-mediated changes in the electrophysiological properties of CA1 pyramidal cells of the hippocampus were also evaluated. In mGlu5a receptor transfected cells, CBPG behaved as a partial agonist, while in mGlu1alpha receptor transfected cells, it behaved as a glutamate antagonist. No effect was found on cAMP formation in cells transfected with mGlu2 receptors or mGlu4 receptors. In brain slices, CBPG neither affected phospholipase D-coupled glutamate receptors nor did it modify the responses to ionotropic receptor stimulation (at concentrations up to 1 mM). When tested in CA1 pyramidal cells of the hippocampus, CBPG (50-100 microM) caused depolarization, increased cell input resistance, and decreased action potential frequency adaptation and afterhyperpolarization. DHPG (3-100 microM), an agonist of both mGlu1 and mGlu5 receptors, and CHPG (1000 microM), a low affinity mGlu5 agonist, produced qualitatively similar effects. The actions of CBPG or CHPG were not modified by AIDA (300 microM), a selective mGlu1 receptor antagonist. Our results suggest that CBPG could be a useful tool for discriminating between mGlu1 receptor and mGlu5 receptor effects and that mGlu5 receptors are the receptors which are mainly responsible for the direct excitatory effects of mGlu receptor agonists on CA1 pyramidal cells.

Extracellular adenosine concentrations during in vitro ischaemia in rat hippocampal slices.

1. The application of an ischaemic insult in hippocampal slices results in the depression of synaptic transmission, mainly attributed to the activation of A1 adenosine receptors by adenosine released in the extracellular space. 2. To estimate the concentration of endogenous adenosine acting at the receptor level during an ischaemic episode, we recorded field e.p.s.ps (fe.p.s.ps) from hippocampal slices, and evaluated the ability of the selective A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), to reverse the fe.p.s.p. depression induced by in vitro ischaemia. A relationship between the IC50 of an antagonist and the endogenous concentration of a neurotransmitter has been used for pharmacological analysis. 3. The complete and reversible depression of fe.p.s.p. in the CA1 region induced by 5 min ischaemia was decreased in the presence of DPCPX (50-500 nM). 8-Phenyltheophylline (10 microM) abolished the depression of fe.p.s.ps during the ischaemic period, while a small (peak effect 12 +/- 4%) decrease in fe.p.s.ps was observed during the initial phase of reperfusion. 4. In the time-interval of maximal depression of fe.p.s.ps., IC50 and adenosine concentration changed as function of time with a good degree of correlation. The maximal value of adenosine concentration was 30 microM. 5. Our data provide an estimation of the adenosine concentration reached at the receptor level during an ischaemic episode, with a higher time discrimination (15 s) than that achieved with any biochemical approach. This estimation may be useful in order to establish appropriate concentrations of purinergic compounds to be tested for their pharmacological effects during an ischaemic episode.

Tryptophan metabolism and hepatic encephalopathy. Studies on the sedative properties of oxindole.

Oxindole administration (1-100 mg/kg i.p.) to mammals decreases locomotor activity, reduces muscular tone and blood pressure and at larger doses causes coma and death. Utilizing both HPLC and GC/MS, we showed that oxindole is present in the blood, brain and other organs of several animal species, including humans. We demonstrated that oxindole is a tryptophan metabolite able to significantly decrease neuronal excitability by modifying the function of voltage-operated sodium channels. Its synthesis requires the availability of indole, which is formed in the gut. When liver function is impaired, a sufficient amount of indole reaches systemic circulation and is oxidized into oxindole, which seems to be one of the responsible agents for the neurological symptoms found in the course of liver impairment.

Electrophysiological effects of felbamate.

Felbamate is a broad spectrum antiepileptic drug recently introduced into clinical practice for controlling seizures in patients affected by Lennox-Gastaut epilepsy, complex partial seizures or otherwise intractable epilepsies. However, the cellular mechanisms by which the drug exerts its anticonvulsant actions are not fully understood. The aim of the present article is to outline the possible mechanisms of action of felbamate as suggested by findings obtained with electrophysiological approaches.

Effect of the selective 5-HT1A receptor antagonist WAY 100635 on the inhibition of e.p.s.ps produced by 5-HT in the CA1 region of rat hippocampal slices.

1. The actions of N-(2-(-4(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl) cyclohexane carboxamide (WAY 100635), a novel and selective 5-hydroxytryptamine1A (5-HT1A) antagonist, on excitatory postsynaptic potentials (e.p.s.ps) were investigated by use of intracellular recordings in pyramidal cells of the CA1 region of rat hippocampal slices. 2. WAY 100635 (10 nM) did not affect any of the investigated parameters of cell excitability such as membrane potential, total input resistance (Rin), firing threshold, action potential amplitude, action potential frequency adaptation, and slow afterhyperpolarization (sAHP) which follows repetitive firing of action potentials. WAY 100635 did not have any effect on either the slope or the amplitude of e.p.s.ps evoked by stimulation of the CA1 stratum radiatum. 3. Bath application of either 5-hydroxytryptamine (5-HT, 10-30 microM) or 5-carboxamidotryptamine (5-CT, 300 nM) hyperpolarized the membrane potential (deltaVm = -4.1 +/- 0.9 and -6.0 +/- 0.9 mV, respectively), and reduced Rin (-25 +/- 8% and -18 +/- 1%, respectively). 5-HT blocked the action potential frequency adaptation and significantly reduced the amplitude of the sAHP that follows repetitive firing of action potentials. 4. 5-HT significantly decreased the amplitude of evoked e.p.s.ps (-14 +/- 6%). This effect was greater in the presence of the GABA(A) receptor antagonist bicuculline (10 microM, -45 +/- 12%) and was mimicked by 5-CT (-49 +/- 5%). Both AMPA and NMDA components of e.p.s.ps were significantly reduced in amplitude by 5-HT (-38 +/- 8%, n = 6, and -29 +/- 12%, n = 3, respectively; P < 0.05). 5. WAY 100635 fully antagonized the hyperpolarization, the reduction of Rin, and the decrease in amplitude of e.p.s.ps elicited by 5-HT, while it did not affect the action of 5-HT on the action potential frequency adaptation. In the presence of WAY 100635, 5-HT elicited a depolarization which was blocked by 10-30 microM RS 23597-190, a selective 5-HT4 receptor antagonist. 6. Our data demonstrate that WAY 100635 is devoid of direct effects on CA1 pyramidal cell excitability and on evoked e.p.s.ps, while it fully antagonizes the effects of 5-HT on excitatory synaptic transmission and on hyperpolarization, without affecting the 5-HT4 receptor-mediated response. Since WAY 100635 selectively antagonizes 5-HT1A receptor-mediated actions of 5-HT, our data also demonstrate that the inhibitory action of 5-HT on excitatory synaptic transmission in CA1 is mediated by 5-HT1A receptors.

Temporal correlation between adenosine outflow and synaptic potential inhibition in rat hippocampal slices during ischemia-like conditions.

The temporal correlation between adenosine outflow and changes in field excitatory post synaptic potentials (fEPSP) occurring during ischemia-like conditions was investigated in rat hippocampal slices. Five-minute long ischemia-like conditions resulted in a 100% depression of fEPSP amplitude, followed by a complete recovery after 6-7 min of reperfusion. By reducing the duration of the ischemic insult to 2 min, fEPSP was depressed by 50%. During both 5 and 2 min of ischemia-like conditions, a significant increase in adenosine outflow was detected. During reperfusion, when fEPSP amplitude recovered completely, the adenosine level in the extracellular fluid returned to basal values. The strict relationship between the increase in adenosine outflow and fEPSP inhibition supports the hypothesis that adenosine is largely responsible for the synaptic transmission depression during cerebral ischemia.

Antagonist properties of (-)-pindolol and WAY 100635 at somatodendritic and postsynaptic 5-HT1A receptors in the rat brain.

1. The aim of the present work was to characterize the 5-hydroxytryptamine1A (5-HT1A) antagonistic actions of (-)-pindolol and WAY 100635 (N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl) cyclohexane carboxamide). Studies were performed on 5-HT1A receptors located on 5-hydroxytryptaminergic neurones in the dorsal raphe nucleus (DRN) and on pyramidal cells in the CA1 and CA3 regions of the hippocampus in rat brain slices. 2. Intracellular electrophysiological recording of CA1 pyramidal cells and 5-hydroxytryptaminergic DRN neurones showed that the 5-HT1A receptor agonist 5-carboxamidotryptamine (5-CT) evoked in both cell types a concentration-dependent cell membrane hyperpolarization and a decrease in cell input resistance. On its own, (-)-pindolol did not modify the cell membrane potential and resistance at concentrations up to 10 microM, but it antagonized the 5-CT effects in a concentration-dependent manner. Similar antagonism of 5-CT effects was observed in the CA3 hippocampal region. (-)-Pindolol also prevented the 5-HT1A receptor-mediated hyperpolarization of CA1 pyramidal cells due to 5-HT (15 microM). In contrast, the 5-HT-induced depolarization mediated by presumed 5-HT4 receptors persisted in the presence of 3 microM (-)-pindolol. 3. In the hippocampus, (-)-pindolol completely prevented the hyperpolarization of CA1 pyramidal cells by 100 nM 5-CT (IC50=92 nM; apparent KB=20.1 nM), and of CA3 neurones by 300 nM 5-CT (IC50=522 nM; apparent KB= 115.1 nM). The block by (-)-pindolol was surmounted by increasing the concentration of 5-CT, indicating a reversible and competitive antagonistic action. 4. Extracellular recording of the firing rate of 5-hydroxytryptaminergic neurones in the DRN showed that (-)-pindolol blocked, in a concentration-dependent manner, the decrease in firing elicited by 100 nM 5-CT (IC50=598 nM; apparent KB= 131.7 nM) or 100 nM ipsapirone (IC50= 132.5 nM; apparent KB= 124.9 nM). The effect of (-)-pindolol was surmountable by increasing the concentration of the agonist. Intracellular recording experiments showed that 10 microM (-)-pindolol were required to antagonize completely the hyperpolarizing effect of 100 nM 5-CT. 5. In vivo labelling of brain 5-HT1A receptors by i.v. administration of [3H]-WAY 100635 ([O-methyl-3H]-N-(2-(4-(2-methoxyphenyl)-1 -piperazinyl)ethyl-N-(2-pyridyl)cyclo-hexane-carboxamide) was used to assess their occupancy following in vivo treatment with (-)-pindolol. (-)-Pindolol (15 mg kg[-1]) injected i.p. either subchronically (2 day-treatment before i.v. injection of [3H]-WAY 100635) or acutely (20 min before i.v. injection of [3H]-WAY 100635) markedly reduced [3H]-WAY 100635 accumulation in all 5-HT1A receptor-containing brain areas. In particular, no differences were observed in the capacity of (-)-pindolol to prevent [3H]-WAY 100635 accumulation in the DRN and the CAI and CA3 hippocampal areas. 6. Intracellular electrophysiological recording of 5-hydroxytryptaminergic DRN neurones showed that WAY 100635 prevented the hyperpolarizing effect of 100 nM 5-CT in a concentration-dependent manner (IC50=4.9 nM, apparent KB=0.25 nM). In CA1 pyramidal cells, hyperpolarization induced by 50 nM 5-CT was also antagonized by WAY 100635 (IC50 = 0.80 nM, apparent KB= 0.28 nM).

Electrophysiological studies on oxindole, a neurodepressant tryptophan metabolite.

1. The aim of the present work was to investigate the electrophysiological effects of oxindole, a tryptophan metabolite present in rat blood and brain, and recently proposed as a contributing factor in the pathogenesis of hepatic encephalopathy. 2. Using rat hippocampal slices in vitro and extra- or intracellular recordings, we evaluated oxindole effects on the neurotransmission of the CA1 region following orthodromic stimulation of the Schaffer collaterals. 3. Oxindole (0.3-3 mM) decreased the amplitude of population spikes extracellularly recorded at the somatic level and of the fEPSPs recorded at the dendritic level. In intracellular recordings, oxindole (0.1-3 mM) did not affect the resting membrane potential or the neuronal input resistance, but reduced the probability of firing action potentials upon either synaptic or direct activation of the pyramidal cells. 4. Oxindole (0.3-3 mM) increased the threshold and the latency of firing action potentials elicited by depolarizing steps without changing the duration or the peak amplitude of the spikes. It also significantly increased the spike frequency adaptation induced by long lasting (400 ms) depolarizing stimuli. 5. In separate experiments, performed by measuring AMPA or NMDA-induced responses in cortical slices, oxindole (1-3 mM) did not modify glutamate receptor agonist responses. 6. Our results show that concentrations of oxindole which may be reached in pathological conditions, significantly decrease neuronal excitability by modifying the threshold of action potential generation.

Felbamate decreases synaptic transmission in the CA1 region of rat hippocampal slices.

The antiepileptic drug felbamate (FBM) is known to block N-methyl-D-aspartate receptor-mediated responses and to decrease voltage-sensitive Na+ and Ca+2 channels. The present work was aimed at investigating the actions of FBM on synaptic potentials in the hippocampus, a region frequently involved in epileptic discharges. In rat hippocampal slices, application of FBM (100-1300 microM, 10 min) elicited a concentration-dependent, fully reversible decrease in amplitude of electrically evoked population spikes recorded extracellularly from the CA1 pyramidal cell layer. In intracellular recordings, FBM (50-300 microM) decreased the amplitude of excitatory postsynaptic potentials and reduced the probability of firing action potentials upon synaptic activation. Action potential frequency adaptation (accommodation), which typically limits repetitive firing in CA1 pyramidal cells, was increased. By using a paired-pulse protocol, FBM (300 microM) depressed the amplitude of paired excitatory postsynaptic potentials, without affecting the facilitation of the second response. In nominally Mg(+2)-free solution, FBM (100 microM) blocked N-methyl-D-aspartate receptor-mediated synaptic excitatory postsynaptic potentials isolated by the presence of 10 microM 6-nitro-7-sulfamoylbenzo(f)quinoxaline hydrochloride, a selective alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist, and 10 microM bicuculline or 25 microM picrotoxin. This effect was not reversed by the addition of 300 microM Gly. All these effects contribute to decrease excitatory synaptic transmission and are likely to limit neuron recruitment and propagation of epileptic discharges.

Electrophysiological effects of N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl) cyclohexane carboxamide (WAY 100635) on dorsal raphe serotonergic neurons and CA1 hippocampal pyramidal cells in vitro.

The aim of the present study was to examine the effects of N-(2-(4-2-methoxphenyl)-1-piperazinyl)ethyl)-N-(2-pyridnyl) cyclohexane carboxamide (WAY 100635) on 5-HT1A receptor-mediated responses in the dorsal raphe nucleus (DRN) and the CA1 hippocampal region. In DRN slices superfused with WAY 100635 (10 nM), the majority of putative 5-HT neurons increased their firing rate (13 +/- 2% of baseline rate). In addition, WAY 100635 completely prevented the decrease in firing rate produced by 5-HT (3-15 microM), 8-OH-DPAT (10 nM), 5-carboxamidotryptamine (20 nM) and lesopitron (100 nM). The antagonism exerted by WAY 100635 (IC50 = 0.95 +/- 0.12 nM against 15 microM 5-HT) was fully surmounted by increasing the concentration of 5-HT to 300 microM. In hippocampal slices, WAY 100635 (0.5-10 nM) did not alter the resting membrane potential or the membrane input resistance of intracellularly recorded CA1 pyramidal cells. However, WAY 100635 completely prevented (IC50 = 0.9-1.7 nM) the hyperpolarization and the decrease in membrane input resistance produced by 5-HT (15-30 microM) and by 5-carboxamidotryptamine (50-300 nM). In contrast, WAY 100635 affected neither the block of action potential frequency adaptation and slow afterhyperpolarization produced by 5-HT (15 microM) nor the hyperpolarization and decrease in membrane input resistance evoked by bath application of GABA(B) receptor agonist baclofen (10 microM). The cumulative concentration-hyperpolarization curve for 5-carboxamidotryptamine (3 nM-10 microM) was shifted to the right by WAY 100635 (apparent Kb = 0.23 +/- 0.07 nM), and the latter drug also reduced the maximal response to the agonist. These data show the WAY 100635 is a potent antagonist at 5-HT1A receptors, both in the DRN and in the CA1 region of the hippocampus. The antagonism is apparently competitive in the DRN and partly noncompetitive in the hippocampus. Kinetic characteristics of the antagonist-receptor interactions might account for these regional differences.