Nitrated alpha-synuclein-activated microglial profiling for Parkinson's disease

Microglial neuroinflammatory processes play a primary role in dopaminergic neurodegeneration for Parkinson's disease (PD). This can occur, in part, by modulation of glial function following activation by soluble or insoluble modified alpha-synuclein (alpha-syn), a chief component of Lewy bodies that is released from affected dopaminergic neurons. alpha-Syn is nitrated during oxidative stress responses and in its aggregated form, induces inflammatory microglial functions. Elucidation of these microglial function changes in PD could lead to new insights into disease mechanisms. To this end, PD-associated inflammation was modeled by stimulation of microglia with aggregated and nitrated alpha-syn. These activated microglia were ameboid in morphology and elicited dopaminergic neurotoxicity. A profile of nitrated, aggregated alpha-syn-stimulated microglia was generated using combinations of genomic (microarrays) and proteomic (liquid chromatography-tandem mass spectrometry, differential gel electrophoresis, and protein array) assays. Genomic studies revealed a substantive role for nuclear factor-kappa B transcriptional activation. Qualitative changes in the microglial proteome showed robust increases in inflammatory, redox, enzyme, and cytoskeletal proteins supporting the genomic tests. Autopsy brain tissue acquired from substantia nigra and basal ganglia of PD patients demonstrated that parallel nuclear factor-kappa B-related inflammatory processes were, in part, active during human disease. Taken together, the transcriptome and proteome of nitrated alpha-syn activated microglia, shown herein, provide new potential insights into disease mechanisms.

Genomic and proteomic microglial profiling: pathways for neuroprotective inflammatory responses following nerve fragment clearance and activation

Microglia, a primary immune effector cell of the central nervous system (CNS) affects homeostatic, neuroprotective, regenerative and degenerative outcomes in health and disease. Despite these broad neuroimmune activities linked to specific environmental cues, a precise cellular genetic profile for microglia in the context of disease and repair has not been elucidated. To this end we used nucleic acid microarrays, proteomics, immunochemical and histochemical tests to profile microglia in neuroprotective immune responses. Optic and sciatic nerve (ON and SN) fragments were used to stimulate microglia in order to reflect immune consequences of nervous system injury. Lipopolysaccharide and latex beads-induced microglial activation served as positive controls. Cytosolic and secreted proteins were profiled by surface enhanced laser desorption ionization-time of flight (SELDI-TOF) ProteinChip, 1D and 2D difference gel electrophoresis. Proteins were identified by peptide sequencing with tandem mass spectrometry, ELISA and western blot tests. Temporal expression of pro-inflammatory cytokines, antioxidants, neurotrophins, and lysosomal enzyme expression provided, for the first time, a unique profile of secreted microglia proteins with neuroregulatory functions. Most importantly, this molecular and biochemical signature supports a broad range of microglial functions for debris clearance and promotion of neural repair after injury.

Ion channel blockade attenuates aggregated alpha synuclein induction of microglial reactive oxygen species: relevance for the pathogenesis of Parkinson's disease

Brain mononuclear phagocyte (perivascular macrophage and microglia, MG) inflammatory neurotoxins play a principal role in the pathogenesis of Parkinson's disease; chief among these are reactive oxygen species (ROS). We posit that aggregated, misfolded and oxidized alpha-synuclein (a major constituent of Lewy bodies), released or secreted from dying dopaminergic neurons, induces microglial ROS production that is regulated by ion channels and as such affects disease progression. To address this hypothesis, we performed patch clamp recordings of outward ionic currents in murine microglia and characterized their links to ROS production during alpha-synuclein stimulation. Aggregated nitrated alpha-synuclein induced ROS production in a dose-dependent manner that was inhibited by voltage-gated potassium current blockade, and to a more limited degree, by chloride current blockade. Interestingly, ROS produced in MG primed with tumor necrosis factor alpha and activated with phorbol myristate acetate was attenuated by voltage-gated potassium current blockade and more completely by chloride current blockade. In contrast, amyloid beta or cell membrane extract failed to induce microglial ROS production. Similar results were obtained using bone marrow-derived macrophages. The association of ROS production with specific plasma membrane ion currents provides a link between regulation of microglial ion transport and oxygen free radical production. Understanding these linkages may lead to novel therapeutics for Parkinson's disease where modulation of redox-related stress may slow disease progression.

Structure-based discovery and optimization of potential cancer therapeutics targeting the cell cycle

Progress has been made recently in the structure-based optimization of novel cell cycle antitumor therapeutics based on cyclin-dependent kinase (CDK) inhibition. A novel inhibitor series based on the 2-amino-4-heteroaryl-pyrimidine scaffold was discovered using the LIDAEUS high-throughput docking methodology, and was subsequently optimized for CDK2 potency through information provided by crystallographic complex structures. A computational study of CDK4 inhibitors led to the incorporation of selectivity determinants into a pyrimidine pharmacophore to generate isoform-specific inhibitors. In addition, molecules from the inhibitor series have been crystallized in complex structures with both monomeric inactive CDK2 and an active complex of CDK2 bound to cyclin A or E. This crystallization revealed that significant differences exist in the affinity of the inhibitors for active and inactive states of CDK2. Information on differences in affinity facilitates the prediction of experimental binding of inhibitors and allows for the further development of structure-guided design.

Protein structures in virtual screening: a case study with CDK2

The influence of protein structure on the successful reproduction of known ligand poses by high-throughput docking programs is rarely discussed. Two commonly used programs, Glide and GOLD, were used to dock a set of CDK2 inhibitors of known bound pose into 20 different CDK2 structures. The numbers of docked poses that reproduced the known pose are reported. Depending on the program and protein structure, 0.3%-96.2% of the ligands docked with the correct pose. Although it is not possible to say that any one structure is "the best" for virtual screening, there are some structures that are clearly better than others. The main determinants of this are the volume of the binding site into which the ligands are docked and the exact orientation of the residues forming the binding site.

Mononuclear phagocytes in the pathogenesis of neurodegenerative diseases

Brain mononuclear phagocytes (MP, bone marrow monocyte-derived macrophages, perivascular macrophages, and microglia) function to protect the nervous system by acting as debris scavengers, killers of microbial pathogens, and regulators of immune responses. MP are activated by a variety of environmental cues and such inflammatory responses elicit cell injury and death in the nervous system. MP immunoregulatory responses include secretion of neurotoxic factors, mobilization of adaptive immunity, and cell chemotaxis. This incites tissue remodelling and blood-brain barrier dysfunction. As disease progresses, MP secretions engage neighboring cells in a vicious cycle of autocrine and paracrine amplification of inflammation leading to tissue injury and ultimately destruction. Such pathogenic processes tilt the balance between the relative production of neurotrophic and neurotoxic factors and to disease progression. The ultimate effects that brain MP play in disease revolves "principally" around their roles in neurodegeneration. Importantly, common functions of brain MP in neuroimmunity link highly divergent diseases (for example, human immunodeficiency virus type-one associated dementia, Alzheimer's disease and Parkinson's disease). Research into this process from our own laboratories and those of others seek to harness MP inflammatory processes with the intent of developing therapeutic interventions that block neurodegenerative processes and improve the quality of life in affected people.

Suppression of L-type voltage-gated calcium channel-dependent synaptic plasticity by ethanol: analysis of miniature synaptic currents and dendritic calcium transients

Intoxicating concentrations of ethanol inhibit N-methyl-d-aspartate (NMDA) receptor-dependent long-term potentiation, an interaction thought to underlie a major component of the central nervous system actions of ethanol. Another form of synaptic potentiation involving activation of L-type dihydropyridine-sensitive voltage-gated calcium channels (VGCCs) has been described, but very little information concerning ethanol effects on VGCC-dependent synaptic potentiation is available. Here, we assessed ethanol effects on VGCC-dependent synaptic potentiation using whole cell patch-clamp recordings of alpha-amino-3-hydroxy-5-methyl-4-soxazolepropionic acid (AMPA) receptor-mediated miniature excitatory postsynaptic currents (mEPSCs) in area CA1 of the rat hippocampus. No potentiation was observed in artificial cerebrospinal fluid containing 2 to 3 mM Ca2+, but marked potentiation of mEPSCs was consistently observed in 4 mM Ca2+ and with patch pipettes containing an ATP-regenerating system. This potentiation was insensitive to the NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid, whereas it was completely blocked the L-type VGCC antagonist nifedipine. Potentiation was also blocked dose dependently by bath application of ethanol (25-75 mM), which had no effect on baseline mEPSC amplitude or frequency. The synaptic potentiation involved enhancement of both presynaptic and postsynaptic components because significant increases in both the frequency and amplitude of AMPA mEPSCs were observed. Ethanol inhibition of VGCC-dependent synaptic potentiation seemed to occur at the induction step because both the increases in mEPSC frequency and amplitude were affected. To address that question more directly, we used fluorescent imaging of synaptically evoked dendritic calcium events, which displayed a similarly marked ethanol sensitivity. Thus, ethanol modulates fast excitatory synaptic transmission by inhibiting the induction of an NMDA receptor-independent form of synaptic potentiation observed at excitatory synapses on central neurons.

N-cadherin and Cx43alpha1 gap junctions modulates mouse neural crest cell motility via distinct pathways

Our previous studies showed an essential role for connexin 43 or alpha1 connexin (Cx43alpha1) gap junctions in the modulation of neural crest cell motility. Cx43alpha1 gap junctions and N-cadherin containing adherens junctions are expressed in migrating cardiac neural crest cells. Analysis of the N-cadherin knockout (KO) mouse model revealed that N-cadherin is essential for gap junction mediated dye coupling but not for expression of Cx43alpha1 gap junctions in neural crest cells. Time lapse videomicroscopy and motion analysis showed that the motility of N-cadherin KO neural crest cells were altered, but the motility changes differed compared to Cx43alpha1 KO neural crest cells. These observations suggest that the role of N-cadherin in cell motility is not simply mediated via the modulation of Cx43alpha1 mediated cell-cell communication. This was confirmed by a parallel analysis of wnt-1 deficient neural crest cells, which also showed a reduction in dye coupling, and yet no change in cell motility. Analysis of p120 catenin (p120ctn), an Amardillo family protein known to play a role in cell motility, showed that it is colocalized with N-cadherin and Cx43alpha1 in migrating neural crest cells. This subcellular distribution was altered in the N-cadherin and Cx43alpha1 KO neural crest cells. Given these results, we propose that N-cadherin and Cx43alpha1 may modulate neural crest cell motility by engaging in a dynamic cross-talk with the cell's locomotory apparatus through p120ctn signaling.

Thermal dependence of neural activity in the hamster hippocampal slice preparation

1. Neural activity was recorded in an in vitro hamster hippocampal slice preparation while the temperature of the Ringer's solution bathing in the slice was controlled at selected levels. 2. The amplitude of the population spike (action potentials from a group of pyramidal cells) was measured as bath temperature was lowered from 35 degrees C to temperatures where a response could not be evoked. 3. Plots of population spike amplitude versus temperature have bell-shaped curves. The population spikes increased in amplitude as temperature was lowered from 35 degrees C, reached a peak amplitude between 25 and 20 degrees C, and then decreased until a response could not be evoked when temperature was further lowered. 4. These in vitro results obtained in the slice preparation are related to in vivo hippocampal studies. Results are interpreted as consistent with the proposal reviewed here that neural activity in the hippocampus plays a role at specific stages of entrance into and arousal from hibernation.

Modulation of mouse neural crest cell motility by N-cadherin and connexin 43 gap junctions

Connexin 43 (Cx43alpha1) gap junction has been shown to have an essential role in mediating functional coupling of neural crest cells and in modulating neural crest cell migration. Here, we showed that N-cadherin and wnt1 are required for efficient dye coupling but not for the expression of Cx43alpha1 gap junctions in neural crest cells. Cell motility was found to be altered in the N-cadherin-deficient neural crest cells, but the alterations were different from that elicited by Cx43alpha1 deficiency. In contrast, wnt1-deficient neural crest cells showed no discernible change in cell motility. These observations suggest that dye coupling may not be a good measure of gap junction communication relevant to motility. Alternatively, Cx43alpha1 may serve a novel function in motility. We observed that p120 catenin (p120ctn), an Armadillo protein known to modulate cell motility, is colocalized not only with N-cadherin but also with Cx43alpha1. Moreover, the subcellular distribution of p120ctn was altered with N-cadherin or Cx43alpha1 deficiency. Based on these findings, we propose a model in which Cx43alpha1 and N-cadherin may modulate neural crest cell motility by engaging in a dynamic cross-talk with the cell's locomotory apparatus through p120ctn signaling.

Management of acute cardiac failure with mechanical assist: experience with the ABIOMED BVS 5000

BACKGROUND

Mechanical circulatory assist industries have developed ventricular assist devices (VAD) for short-, intermediate-, and long-term use. The purpose of this report is to describe the progress made with the ABIOMED Biventricular System (BVS) 5000 (ABIOMED, Inc, Danvers, MA) short-term VAD.

METHODS

From June 1994 through August 2000, all cardiogenic shock patients who required short-term mechanical assist were supported with the ABIOMED BVS 5000. Insertion criteria included any condition that may potentially result in cardiac recovery. A formal algorithm for timing of insertion was established to standardize implantation criteria.

RESULTS

A total of 45 patients were supported at Hahnemann University Hospital, Philadelphia, PA. There were 26 male and 19 female patients, with a mean age of 57.9 years (range 33 to 80 years). Devices were inserted for postcardiotomy shock in 36 patients (80%) and precardiotomy shock in 9 patients (20%). The average duration of support was 8.3 days (range 1 to 31 days). Overall, there were 22 (49%) patients weaned from support and 14 (31%) discharged from the hospital. For patients in whom the device was implanted in accordance with an established protocol (group A), the wean and discharge rates were 60% and 43%, respectively. The most common morbidities included bleeding and adverse neurologic events.

CONCLUSIONS

The ABIOMED BVS 5000 VAD continues to be a valuable form of short-term mechanical assist for acute cardiogenic shock. The formation of a uniform VAD insertion algorithm has helped to standardize protocols in management.

Compliance issues related to the selection of antibiotic suspensions for children

OBJECTIVE

To evaluate the palatability, cost and other compliance issues as variables in the selection of antibiotic suspensions for children.

METHODS

Eighty-six physicians and health care personnel randomly sampled amoxicillin (used as a standard for comparison) and 11 other antibiotics, evaluating them in categories of appearance, smell, texture, taste and aftertaste. Overall scoring was then adjusted for cost, duration of therapy and dosing intervals.

RESULTS

Overall taste (palatability) ranking of antibiotics, highest to lowest, was as follows: loracarbef, cefdinir, cefixime, azithromycin, ciprofloxacin, trimethoprim-sulfamethoxazole, clarithromycin, trimethoprim, amoxicillin/clavulanate, cefpodoxime and cefuroxime. Overall rating of antibiotics was greatly influenced by other compliance variables, in order of their impact: cost; duration of therapy (5 vs. 10 days); and dosing intervals. Cost was not judged to be a major factor by most participants unless antibiotic expense was >$50.00 for treatment of otitis media in our hypothetical 2-year-old, 13-kg child. Taking all variables into consideration, final ranking from highest to lowest was azithromycin, cefdinir, loracarbef, cefixime, amoxicillin, trimethoprim-sulfamethoxazole, cefpodoxime, trimethoprim, clarithromycin, ciprofloxacin, cefuroxime and amoxicillin/clavulanate.

CONCLUSIONS

Variables related to compliance for families filling antibiotic prescriptions and children taking these products are important in the selection of antimicrobial therapy. Because final assessment is likely to vary considerably among health care personnel, decisions must be made on an individual basis.

Dynamics of NMDAR-mediated neurotoxicity during chronic ethanol exposure and withdrawal

We have utilized a hippocampal brain slice explant system to assess cellular and synaptic mechanisms underlying the expression of alcohol withdrawal hyperexcitability. Previously, we observed a role for NMDA receptors in the expression of electrographic seizures (EGS) observed immediately upon withdrawal from chronic ethanol exposure in this system. One possible cellular mechanism responsible for these prior results involves NMDAR-mediated neurotoxicity, which was assessed in the present study. Explants were exposed to 35 or 75 mM ethanol for 6 or 12 days and incubated with propidium iodide (PI) to label non-viable cells and then imaged digitally. PI labeling was significantly reduced (36% of control levels) following chronic ethanol exposure (75 mM). When tested following ethanol withdrawal, PI labeling remained significantly reduced in the 75 mM exposed group. We next assessed the effect of an NMDA challenge 24 h following withdrawal. The 35 mM and 75 mM ethanol exposed groups displayed significant 6-fold and 13-fold NMDAR-mediated increases in PI labeling respectively; control explants displayed a 3-fold increase. These data suggest that chronic ethanol exposure prior to withdrawal has a minor neuroprotective effect that slightly diminishes within 24 h of ethanol withdrawal. Furthermore, the data indicate that direct NMDAR activation is required for induction of ethanol withdrawal neurotoxicity.

Structural analysis of a mutational hot-spot in the EcoRV restriction endonuclease: a catalytic role for a main chain carbonyl group

Following random mutagenesis of the Eco RV endonuclease, a high proportion of the null mutants carry substitutions at Gln69. Such mutants display reduced rates for the DNA cleavage step in the reaction pathway, yet the crystal structures of wild-type Eco RV fail to explain why Gln69 is crucial for activity. In this study, crystal structures were determined for two mutants of Eco RV, with Leu or Glu at residue 69, bound to specific DNA. The structures of the mutants are similar to the native protein and no function can be ascribed to the side chain of the amino acid at this locus. Instead, the structures of the mutant proteins suggest that the catalytic defect is due to the positioning of the main chain carbonyl group. In the enzyme-substrate complex for Eco RV, the main chain carbonyl of Gln69 makes no interactions with catalytic functions but, in the enzyme-product complex, it coordinates a metal ion bound to the newly liberated 5'-phosphate. This re-positioning may be hindered in the mutant proteins. Molecular dynamics calculations indicate that the metal on the phosphoryl oxygen interacts with the carbonyl group upon forming the pentavalent intermediate during phosphodiester hydrolysis. A main chain carbonyl may thus play a role in catalysis by Eco RV.

Coronary artery disease in identical twins

The incidence of coronary artery disease in identical twins is unknown. The knowledge of ischemic heart disease in this patient population is represented by case reports. There is considerable controversy regarding the environmental and genetic factors that play a role in the pathogenesis of this disorder. The natural history of coronary artery disease in an asymptomatic twin with a symptomatic counterpart is unclear. We present a case report and literature review of coronary artery disease in identical twins. On the basis of our patient and the information of other patients, asymptomatic twins of symptomatic counterparts require aggressive assessment and management for occult coronary artery disease.

Coronary artery bypass surgery in nonagenarians

As the number of nonagenarians increases yearly in the United States, surgeons will be asked more often to evaluate the possibility of intervention for coronary artery disease in this age group. The purpose of this study is to document experience with patients 90 years of age or older in order to determine whether coronary artery bypass grafting surgery is justified. Eleven patients aged 90 years or more underwent cardiac surgery for symptomatic coronary artery disease refractory to medical management between January 1, 1987, and December 31, 1996. All patients were in NYHA Class IV preoperatively. In-hospital death occurred in two patients (18%). In-hospital morbidity occurred in all patients (100%) including seven cardiac, four respiratory, two neurologic, and one infectious. All survivors left the hospital symptomatically improved. The mean length of stay was 28 days. Four patients died at a mean of 2 years and 2 months postoperatively. Five patients remain alive at a mean of 1 year and 7 months. Coronary artery bypass grafting in nonagenarians can be performed successfully in selected cases. However, increased mortality and morbidity rates and length of stay are associated with this age group. For survivors, the quality of life is improved and the projected life expectancy restored.

Pharmacological criteria for ventricular assist device insertion following postcardiotomy shock: experience with the Abiomed BVS system

BACKGROUND/AIM

The traditional approach to postcardiotomy shock includes inotropic support followed by the application of an intra-aortic balloon pump (IABP). Consideration toward insertion of a ventricular assist device (VAD) becomes necessary when these maneuvers fail to restore hemodynamic stability. The definition of maximal inotropic support, however, is lacking such that a standard formula for VAD insertion remains problematic. The purpose of this paper is to define the pharmacological thresholds for VAD implantation in the setting of postcardiotomy cardiogenic shock.

METHODS

The medical records of all adult open-heart operations performed at Hahnemann University Hospital, Philadelphia, PA, from 1 July 1996 through 1 July 1999 were reviewed. Specific data were collected on the hemodynamics and inotrope levels upon separation from cardiopulmonary bypass (CPB). The hospital course was reviewed with attention toward documenting hospital mortality. Cardiogenic shock was defined as systolic blood pressure (SBP) < 100 mmHg, mean pulmonary artery blood pressure (mPAP) > 25 mmHg, central venous pressure (CVP) > 15 mmHg, and cardiac index (CI) < 2.0 L/min/per m2. Inotrope dosages were defined as low, moderate, and high according to assigned values. A formula for VAD insertion was established if cardiogenic shock parameters were present in the setting of two or more high dose inotropes. Early VAD insertion was defined as implantation within three hours of the first attempt to wean from CPB. The VAD recipients were divided into two groups. Group A were VADs placed in conjunction with the formula. Group B was VADs placed in violation (excess) of the formula. The results of these two groups were compared. [table: see text]

RESULTS

From 1 July 1996 to 1 July 1999, there were 3462 adult open-heart operations performed at Hahnemann University Hospital, Philadelphia, Pa. The hospital mortality for patients successfully separating from CPB on no inotropes, low-dose, moderate-dose, one high-dose, two high-dose, and three high-dose inotropes were approximately 2.0%, 3.0%, 7.5%, 21%, 42%, and 80% respectively. During this time there were 29 patients supported with the Abiomed BVS (Danvers, Mass) system for postcardiotomy cardiogenic shock. For the entire group of VAD recipients, there were 18 (62%) who were successfully weaned and 8 (28%) who were discharged from the hospital. For the 20 VAD recipients in group A, there were 16 (80%) who were successfully weaned and 8 (40%) who were discharged from the hospital. For the nine VAD recipients in group B, there were two (22%) who were successfully weaned and zero (0%) who were discharged from the hospital. Multiple organ system failure occurred in three (15%) in group A versus seven (78%) in group B patients, respectively. Early VAD insertion was accomplished in 17 (85%) group A patients and 2 (22%) group B patients.

CONCLUSIONS

Hospital mortality correlates with the number and level of inotropic support necessary to separate from CPB following adult open heart surgery. The application of a standard pharmacological formula together with hemodynamic criteria for VAD insertion after postcardiotomy cardiogenic shock results in earlier insertion, lower incidence of postoperative MOSF, and improved wean and discharge rates.

Amiodarone-associated hemoptysis

Amiodarone is a benzofuran derivative with a chemical structure similar to thyroxine. Originally introduced to treat angina pectoris, amiodarone was found to have antiarrhythmic properties, and in 1985, was approved in the United States for treatment of life-threatening ventricular arrhythmias. It is now used for various ventricular and supraventricular arrhythmias refractory to conventional first-line medications, and as a result, side effects have been observed with increased frequency. The most severe and potentially life-threatening of these side effects is the development of pulmonary toxicity. Typically, amiodarone pulmonary toxicity (APT) is manifested by acute pneumonitis and chronic fibrosis. Amiodarone-associated hemoptysis (AAH) is a rare occurrence. The authors describe a case of AAH successfully treated with cessation of drug and steroid therapy.

Evidence for a causative role of N-methyl-D-aspartate receptors in an in vitro model of alcohol withdrawal hyperexcitability

Synaptic mechanisms underlying hyperexcitability due to withdrawal from chronic ethanol exposure were investigated in a hippocampal explant model system using electrophysiological techniques. Whole-cell voltage clamp recordings from CA1 pyramidal cells demonstrated that acute ethanol exposure inhibited N-methyl-D-aspartate receptor (NMDAR)-mediated excitatory postsynaptic currents by over 40%. Chronic ethanol exposure for 6 to 11 days at 35 or 75 mM induced no differences from control explants in the fast component of the population synaptic response (non-NMDAR-mediated). Prolonged field potential recordings (to 10 hr) were used to monitor the withdrawal process in vitro. Ethanol-exposed explants from both 35 and 75 mM groups displayed an increase (60% and 89%, respectively) in the NMDAR-mediated component of synaptic transmission on withdrawal from chronic exposure. Prolonged tonic-clonic electrographic seizure activity was consistently observed after ethanol withdrawal only after the increase in NMDAR function. This hyperexcitability was inhibited by the NMDAR antagonist D-2-amino-5-phosphonovaleric acid and returned once the NMDAR component was reestablished after antagonist washout. In situ hybridization studies suggest that expression of NR2B subunit mRNA may be enhanced in explants after chronic ethanol exposure. No lasting differences were observed in the NMDAR component after acute in vitro ethanol exposure and withdrawal. These data suggest that the occurance of ethanol withdrawal hyperexcitability in this system may be directly dependent on alterations in NMDAR function after chronic exposure. Since this region and others that contain ethanol sensitive NMDARs may serve as epileptic foci, long term alterations in NMDAR function may be expected to generate paroxysmal depolarizing shifts underlying ictal events after withdrawal from ethanol exposure.

Survival and functional demonstration of interregional pathways in fore/midbrain slice explant cultures

An important general question in neurobiology concerns the development and expression of the rich context of neuronal phenotypes, especially in relation to the diverse patterns of connectivity. Organotypic cultures of brain slices may offer distinct advantages for such studies if such a preparation survives, maintains a wide diversity of neuronal phenotypes and displays appropriate synaptic connections between regions. To address these requirements, we utilized long-term organotypic cultures of intact horizontal slices of rat forebrain and midbrain and assessed a variety of markers of phenotype in combination with functional tests of connectivity. This explant preparation displayed a distinct viability requirement such that the greatest explant survival was seen in slices taken from pups of less than postnatal day 7 and was independent of N-methyl-D-aspartate channel blockade. The anatomical features of the major brain regions (e.g., neocortex, striatum, septum, hippocampus, diencephalon and midbrain) were observed in their normal boundaries. The presence of cholinergic and catecholaminergic neurons was demonstrated with acetylcholinesterase histochemistry and tyrosine hydroxylase immunohistochemistry. Labelled neurons displayed multiple, regionally-appropriate cytoarchitectures and, in some cases, could be seen to project to brain regions in a manner quite similar to that seen in vivo. Finally, the direct demonstration of spontaneous and evoked interregional excitatory synaptic transmission was made using whole-cell patch-clamp recordings from striatal neurons which revealed an intact glutamate-using corticostriatal pathway. This simple explant preparation appears to contain a rich diversity of neuronal types and synaptic organization. Therefore, this preparation appears to have several distinct advantages for basic neurobiologic research since it combines long-term culture viability and many features of mature brain including complex interregional neuronal systems.