Potentiating KCC2 activity is sufficient to limit the onset and severity of seizures

The type 2 K+/Cl- cotransporter (KCC2) allows neurons to maintain low intracellular levels of Cl-, a prerequisite for efficient synaptic inhibition. Reductions in KCC2 activity are evident in epilepsy; however, whether these deficits directly contribute to the underlying pathophysiology remains controversial. To address this issue, we created knock-in mice in which threonines 906 and 1007 within KCC2 have been mutated to alanines (KCC2-T906A/T1007A), which prevents its phospho-dependent inactivation. The respective mice appeared normal and did not show any overt phenotypes, and basal neuronal excitability was unaffected. KCC2-T906A/T1007A mice exhibited increased basal neuronal Cl- extrusion, without altering total or plasma membrane accumulation of KCC2. Critically, activity-induced deficits in synaptic inhibition were reduced in the mutant mice. Consistent with this, enhanced KCC2 was sufficient to limit chemoconvulsant-induced epileptiform activity. Furthermore, this increase in KCC2 function mitigated induction of aberrant high-frequency activity during seizures, highlighting depolarizing GABA as a key contributor to the pathological neuronal synchronization seen in epilepsy. Thus, our results demonstrate that potentiating KCC2 represents a therapeutic strategy to alleviate seizures.

Postsynaptic adhesion GPCR latrophilin-2 mediates target recognition in entorhinal-hippocampal synapse assembly

Synapse assembly likely requires postsynaptic target recognition by incoming presynaptic afferents. Using newly generated conditional knock-in and knockout mice, we show in this study that latrophilin-2 (Lphn2), a cell-adhesion G protein-coupled receptor and presumptive α-latrotoxin receptor, controls the numbers of a specific subset of synapses in CA1-region hippocampal neurons, suggesting that Lphn2 acts as a synaptic target-recognition molecule. In cultured hippocampal neurons, Lphn2 maintained synapse numbers via a postsynaptic instead of a presynaptic mechanism, which was surprising given its presumptive role as an α-latrotoxin receptor. In CA1-region neurons in vivo, Lphn2 was specifically targeted to dendritic spines in the stratum lacunosum-moleculare, which form synapses with presynaptic entorhinal cortex afferents. In this study, postsynaptic deletion of Lphn2 selectively decreased spine numbers and impaired synaptic inputs from entorhinal but not Schaffer-collateral afferents. Behaviorally, loss of Lphn2 from the CA1 region increased spatial memory retention but decreased learning of sequential spatial memory tasks. Thus, Lphn2 appears to control synapse numbers in the entorhinal cortex/CA1 region circuit by acting as a domain-specific postsynaptic target-recognition molecule.

The effects of amyloid precursor protein on postsynaptic composition and activity

The amyloid precursor protein (APP) is cleaved to produce the Alzheimer disease-associated peptide Abeta, but the normal functions of uncleaved APP in the brain are unknown. We found that APP was present in the postsynaptic density of central excitatory synapses and coimmunoprecipitated with N-methyl-d-aspartate receptors (NMDARs). The presence of APP in the postsynaptic density was supported by the observation that NMDARs regulated trafficking and processing of APP; overexpression of the NR1 subunit increased surface levels of APP, whereas activation of NMDARs decreased surface APP and promoted production of Abeta. We transfected APP or APP RNA interference into primary neurons and used electrophysiological techniques to explore the effects of APP on postsynaptic function. Reduction of APP decreased (and overexpression of APP increased) NMDAR whole cell current density and peak amplitude of spontaneous miniature excitatory postsynaptic currents. The increase in NMDAR current by APP was due to specific recruitment of additional NR2B-containing receptors. Consistent with these findings, immunohistochemical experiments demonstrated that APP increased the surface levels and decreased internalization of NR2B subunits. These results demonstrate a novel physiological role of postsynaptic APP in enhancing NMDAR function.

Aging delays the regeneration process following sciatic nerve injury in rats

The present study investigated the effect of aging on muscle reinnervation in rats following a crush nerve injury. Using confocal laser scanning microscopy, we examined the spatial correlation of terminal Schwann cells (TSCs) or axon terminals with acetylcholine receptor (AChR) sites at neuromuscular junctions (NMJs). Compared to young rats (4 months of age), aged rats (24 months of age) demonstrated damaged TSC extensions and delayed regeneration. Post-injury endplate abnormalities in aged rats correlated with the degree of TSC degeneration. In the late stages of reinnervation, pathologic changes were seen in old rats, including multiple innervations, terminal sprouting, and poorly formed collateral innervation in NMJs. Our results suggest that the impaired TSC-axon interaction in aged rats delays the reinnervation process.

Abnormalities in neuromuscular junction structure and skeletal muscle function in mice lacking the P2X2 nucleotide receptor

ATP is co-released in significant quantities with acetylcholine from motor neurons at skeletal neuromuscular junctions (NMJ). However, the role of this neurotransmitter in muscle function remains unclear. The P2X2 ion channel receptor subunit is expressed during development of the skeletal NMJ, but not in adult muscle fibers, although it is re-expressed during muscle fiber regeneration. Using mice deficient for the P2X2 receptor subunit for ATP (P2X2(-/-)), we demonstrate a role for purinergic signaling in NMJ development. Whereas control NMJs were characterized by precise apposition of pre-synaptic motor nerve terminals and post-synaptic junctional folds rich in acetylcholine receptors (AChRs), NMJs in P2X2(-/-) mice were disorganized: misapposition of nerve terminals and post-synaptic AChR expression localization was common; the density of post-synaptic junctional folds was reduced; and there was increased end-plate fragmentation. These changes in NMJ structure were associated with muscle fiber atrophy. In addition there was an increase in the proportion of fast type muscle fibers. These findings demonstrate a role for P2X2 receptor-mediated signaling in NMJ formation and suggest that purinergic signaling may play an as yet largely unrecognized part in synapse formation.

Partial reduction of BACE1 has dramatic effects on Alzheimer plaque and synaptic pathology in APP Transgenic Mice

The aspartyl protease beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) initiates processing of amyloid precursor protein (APP) into amyloid beta (Abeta) peptide, the major component of Alzheimer disease (AD) plaques. To determine the role that BACE1 plays in the development of Abeta-driven AD-like pathology, we have crossed PDAPP mice, a transgenic mouse model of AD overexpressing human mutated APP, onto mice with either a homozygous or heterozygous BACE1 gene knockout. Analysis of PDAPP/BACE(-/-) mice demonstrated that BACE1 is absolutely required for both Abeta generation and the development of age-associated plaque pathology. Furthermore, synaptic deficits, a neurodegenerative pathology characteristic of AD, were also reversed in the bigenic mice. To determine the extent of BACE1 reduction required to significantly inhibit pathology, PDAPP mice having a heterozygous BACE1 gene knock-out were evaluated for Abeta generation and for the development of pathology. Although the 50% reduction in BACE1 enzyme levels caused only a 12% decrease in Abeta levels in young mice, it nonetheless resulted in a dramatic reduction in Abeta plaques, neuritic burden, and synaptic deficits in older mice. Quantitative analyses indicate that brain Abeta levels in young APP transgenic mice are not the sole determinant for the changes in plaque pathology mediated by reduced BACE1. These observations demonstrate that partial reductions of BACE1 enzyme activity and concomitant Abeta levels lead to dramatic inhibition of Abeta-driven AD-like pathology, making BACE1 an excellent target for therapeutic intervention in AD.

Rapid synapse elimination after postsynaptic protein synthesis inhibition in vivo

To examine the role of retrograde signals on synaptic maintenance, we inhibited protein synthesis in individual postsynaptic cells in vivo while monitoring presynaptic terminals. Within 12 h, axon terminals begin to atrophy and withdraw from normal postsynaptic sites. Structural similarities between this process and naturally occurring synapse elimination suggest that short-lived target derived factors not only participate in synaptic maintenance in adults, but also regulate elimination of connections during development.

Structural changes at synapses after delayed perfusion fixation in different regions of the mouse brain

We recently showed by electron microscopy that the postsynaptic density (PSD) from hippocampal cultures undergoes rapid structural changes after ischemia-like conditions. Here we report that similar structural changes occur after delay in transcardial perfusion fixation of the mouse brain. Delay in perfusion fixation, a condition that mimics ischemic stress, resulted in 70%, 90%, and 23% increases in the thickness of PSDs from the hippocampus (CA1), cerebral cortex (layer III), and cerebellar cortex (Purkinje spines), respectively. In step with PSD thickening, the amount of PSD-associated alpha-calcium calmodulin-dependent protein kinase II (alpha- CaMKII) label increased more in cerebral cortical spines than in Purkinje spines. Although the Purkinje PSDs thickened only slightly after delayed fixation, they became highly curved, and many formed sub-PSD spheres approximately 80 nm in diameter that labeled for CaMKII. Delayed perfusion fixation also produced more cytoplamic CaMKII clusters ( approximately 110 nm in diameter) in the somas of pyramidal cells (from hippocampus and cerebral cortex) than in Purkinje cells. Thus a short delay in perfusion fixation produces cell-specific structural changes at PSDs and neuronal somas. Purkinje cells respond somewhat differently to delayed perfusion fixation, perhaps owing to their lower levels of CaMKII, and CaMKII binding proteins at PSDs. We present here a catalogue of structural changes that signal a perfusion fixation delay, thereby providing criteria by which to assess perfusion fixation quality in experimental structural studies of brain and to shed light on the subtle changes that occur in intact brain following metabolic stress.

Neuroprotective effect of the surfactant poloxamer 188 in a model of intracranial hemorrhage in rats

OBJECT

Neuronal injury remains a leading cause of morbidity in both neonates and adults with injuries induced by intracranial hemorrhage, ischemia-reperfusion, and excitotoxicity. To date, a number of neuroprotective strategies have been evaluated, but they have shown little benefit. Poloxamer 188 (P-188), a membrane-active triblock copolymer, has been studied extensively as a cell-membrane sealant. The authors used an animal model to study the neuroprotectant effects of P-188 administered by intracisternal (IC) injection after experimentally induced intraparenchymal hemorrhage.

METHODS

Sprague-Dawley rats received an IC injection of either P-188 or vehicle (artificial cerebrospinal fluid) 10 minutes after striatal infusion of 50 microl of autologous blood. Animals from both treatment groups were killed either 2 or 7 days later. In a second experiment, after striatal blood infusion and early IC injection of either P-188 or vehicle, animals received daily IC injections of either P- 188 or vehicle for 5 days, and were killed 7 days after induction of the experimental hemorrhage. Striatal tissues were histologically analyzed for neuronal loss, and lesion volumes were determined. Lesion volumes in the animals that received a single dose of P-188 were significantly smaller (mean+/-standard deviation 18.3+/-4.3 mm(3), six rats; p = 0.04) than those in the control group (31.4+/-4.3 mm(3), seven rats) when measured 2 days postinjection; however, no difference in lesion volumes was present 7 days postinjection. Lesion volumes in the animals who received 5 days of daily P-188 injections were significantly smaller (1.50+/-0.58 mm(3), 10 rats; p = 0.04) than those in the corresponding control group (5.04+/-1.85 mm(3), eight rats) when measured at 7 days.

CONCLUSIONS

A single dose of P- 188 protects against early neuronal loss after hemorrhage but has no effect on long-term hemorrhage-induced neuronal loss. However, repeated daily P-188 treatment appears to produce effective long-term neuronal protection.

Ischemia-induced modifications in hippocampal CA1 stratum radiatum excitatory synapses

Relatively mild ischemic episode can initiate a chain of events resulting in delayed cell death and significant lesions in the affected brain regions. We studied early synaptic modifications after brief ischemia modeled in rats by transient vessels' occlusion in vivo or oxygen-glucose deprivation in vitro and resulting in delayed death of hippocampal CA1 pyramidal cells. Electron microscopic analysis of excitatory spine synapses in CA1 stratum radiatum revealed a rapid increase of the postsynaptic density (PSD) thickness and length, as well as formation of concave synapses with perforated PSD during the first 24 h after ischemic episode, followed at the long term by degeneration of 80% of synaptic contacts. In presynaptic terminals, ischemia induced a depletion of synaptic vesicles and changes in their spatial arrangement: they became more distant from active zones and had larger intervesicle spacing compared to controls. These rapid structural synaptic changes could be implicated in the mechanisms of cell death or adaptive plasticity. Comparison of the in vivo and in vitro model systems used in the study demonstrated a general similarity of these early morphological changes, confirming the validity of the in vitro model for studying synaptic structural plasticity.

A CaV2.1 calcium channel mutationrockerreduces the number of postsynaptic AMPA receptors in parallel fiber-Purkinje cell synapses

The rocker mice are hereditary ataxic mutants that carry a point mutation in the gene encoding the CaV2.1 (P/Q-type) Ca2+ channel alpha1 subunit, and show the mildest symptoms among the reported CaV2.1 mutant mice. We studied the basic characteristics of the rocker mutant Ca2+ channel and their impacts on excitatory synaptic transmission in cerebellar Purkinje cells (PCs). In acutely dissociated PC somas, the rocker mutant channel showed a moderate reduction in Ca2+ channel current density, whereas its kinetics and voltage dependency of gating remained nearly normal. Despite the small changes in channel function, synaptic transmission in the parallel fiber (PF)-PC synapses was severely impaired. The climbing fiber inputs onto PCs showed a moderate impairment but could elicit normal complex spikes. Presynaptic function of the PF-PC synapses, however, was unexpectedly almost normal in terms of paired-pulse facilitation, sensitivity to extracellular Ca2+ concentration and glutamate concentration in synaptic clefts. Electron microscopic analyses including freeze-fracture replica labeling revealed that both the number and density of postsynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors substantially decreased without gross structural changes of the PF-PC synapses. We also observed an abnormal arborization of PC dendrites in young adult rocker mice (approximately 1 month old). These lines of evidence suggest that even a moderate dysfunction of CaV2.1 Ca2+ channel can cause substantial changes in postsynaptic molecular composition of the PF-PC synapses and dendritic structure of PCs.

Chronic restraint stress induces changes in synapse morphology in stratum lacunosum-moleculare CA1 rat hippocampus: a stereological and three-dimensional ultrastructural study

Chronic restraint stress is known to affect the morphology and synaptic organization of the hippocampus, predominantly within CA3 but also in CA1 and dentate gyrus. In this study, we provide the first evidence for specific ultrastructural alterations affecting asymmetric axo-spinous synapses in CA1 stratum lacunosum-moleculare following chronic restraint stress (6 h/day, 21 days) in the rat. The structure of asymmetric axo-spinous post-synaptic densities was investigated using serial section three-dimensional reconstruction procedures in control (n=4) and chronic restraint stress (n=3) animals. Dendritic spine profiles (spine head+neck) associated with the sampled synaptic contacts (30 per animal) were also reconstructed in three-dimensions. Morphometric analyses revealed a significant increase in post-synaptic density surface area (+36%; P=0.03) and a highly significant increase in post-synaptic density volume (+79%; P=0.003) in the chronic restraint stress group. These changes were directly associated with 'non-macular' (perforated, complex and segmented) post-synaptic densities. A highly significant overall increase in the 'post-synaptic density surface area/spine surface area' ratio was also detected in the chronic restraint stress group (+27%; P=0.002). In contrast, no quantitative changes in spine parameters were found between groups. The Cavalieri method was used to assess the effects of chronic restraint stress exposure upon CA1 hippocampal volume. The mean volume of total dorsal anterior CA1 hippocampus was significantly lower in the chronic restraint stress group (-16%; P=0.036). However, when corrected for volume changes, no significant alteration in a relative estimate of the mean number of asymmetric axo-spinous synapses was detected in CA1 stratum lacunosum-moleculare between control and chronic restraint stress groups. The data indicate a structural remodeling of excitatory axo-spinous synaptic connectivity in rat CA1 stratum lacunosum-moleculare as a result of chronic restraint stress.

Decreases in the precision of Purkinje cell pacemaking cause cerebellar dysfunction and ataxia

Episodic ataxia type-2 (EA2) is caused by mutations in P/Q-type voltage-gated calcium channels that are expressed at high densities in cerebellar Purkinje cells. Because P/Q channels support neurotransmitter release at many synapses, it is believed that ataxia is caused by impaired synaptic transmission. Here we show that in ataxic P/Q channel mutant mice, the precision of Purkinje cell pacemaking is lost such that there is a significant degradation of the synaptic information encoded in their activity. The irregular pacemaking is caused by reduced activation of calcium-activated potassium (K(Ca)) channels and was reversed by pharmacologically increasing their activity with 1-ethyl-2-benzimidazolinone (EBIO). Moreover, chronic in vivo perfusion of EBIO into the cerebellum of ataxic mice significantly improved motor performance. Our data support the hypothesis that the precision of intrinsic pacemaking in Purkinje cells is essential for motor coordination and suggest that K(Ca) channels may constitute a potential therapeutic target in EA2.

Synaptic differences in the patch matrix compartments of subjects with schizophrenia: a postmortem ultrastructural study of the striatum

The striatum processes motor, cognitive, and limbic circuitry. Striatal patch and matrix compartments are organized differently in many aspects including connectivity. Abnormalities in either compartment could have different functional consequences. The present study compares the synaptic organization in the patches and matrix in subjects with schizophrenia (SZ, n = 14) versus normal controls (NC, n = 8). Postmortem striatal tissue was processed for calbindin immunocytochemistry to identify the patch versus matrix compartments, prepared for electron microscopy, and analyzed using stereology. Several synaptic changes were observed in the SZ subjects vs. NCs including a higher density of cortical-type synapses in the putamen patch (44% higher) and in the caudate matrix (36% higher) in SZ cases on typical antipsychotic drugs. These changes appeared to be normalized rather than caused by treatment. The abnormal connectivity may represent a failure of normal synaptic pruning and may play a role in limbic or cognitive dysfunction in schizophrenia.

Interaction of huntingtin fragments with brain membranes--clues to early dysfunction in Huntington's disease

Abstract Huntingtin is a large, multi-domain protein of unknown function in the brain. An abnormally elongated polyglutamine stretch in its N-terminus causes Huntington's disease (HD), a progressive neurodegenerative disorder. Huntingtin has been proposed to play a functional role in membrane trafficking via proteins involved in endo- and exocytosis. Here, we supply evidence for a direct association between huntingtin and membranes. In the brains of R6/2 mice with HD pathology, a 64 kDa N-terminal huntingtin fragment accumulated in postsynaptic membranes during the pre-symptomatic period of 4-8 weeks of age. In addition, an oligomeric fragment of approximately 200 kDa was detected at 8 weeks of age. Simultaneous progressive changes in distribution of amphiphysin, synaptojanin, and subunits of NMDA- and AMPA-receptors provide a strong indication of dysfunctional synaptic trafficking. Composition of the major phospholipids in the synaptic membranes was unaffected. In vitro, large unilamellar vesicles of brain lipids readily associated with soluble N-terminal huntingtin exon 1 fragments and stimulated fibrillogenesis of mutant huntingtin aggregates. Moreover, interaction of both mutant and wild-type huntingtin exon 1 fragments with brain lipids caused bilayer perturbation, mediated through a proline-rich region adjacent to the polyglutamines. This suggests that lipid interactions in vivo could influence misfolding of huntingtin and may play an early role in HD pathogenesis.

Regulation of hippocampal synapse remodeling by epileptiform activity

We examined the regulation of dendritic spines and synapses by epileptiform activity (EA) in rat hippocampal slice cultures. EA, which was induced by a GABA(A) receptor inhibitor, gabazine, reduced pyramidal neuron spine density by approximately 50% after 48 h and also caused an increase in the average length of remaining spines. To directly determine the effects of EA on synapses, we used fluorescent protein-tagged PSD95, which marks postsynaptic densities. EA induced a net loss of synapses on spines but not shafts; conversely, activity blockade (TTX) induced a loss of shaft synapses. Time-lapse confocal imaging in live tissue slices revealed that EA (1) shifts the balance of synapse gain and loss in dendrites leading to a net loss of spine synapses and (2) induces the formation of new filopodia-like dendritic structures having abnormally slow motility. These results identify EA-induced changes in the density and distribution of synaptic structures on dendrites.

Using proteomics and network analysis to elucidate the consequences of synaptic protein oxidation in a PS1+AβPP mouse model of Alzheimer's disease

Increasing evidence suggests that oxidative injury is involved in the pathogenesis of many age-related neurodegenerative disorders, including Alzheimer's disease (AD). Identifying the protein targets of oxidative stress is critical to determine which proteins may be responsible for the neuronal impairments and subsequent cell death that occurs in AD. In this study, we have applied a high-throughput shotgun proteomic approach to identify the targets of protein carbonylation in both aged and PS1 + AbetaPP transgenic mice. However, because of the inherent difficulties associated with proteomic database searching algorithms, several newly developed bioinformatic tools were implemented to ascertain a probability-based discernment between correct protein assignments and false identifications to improve the accuracy of protein identification. Assigning a probability to each identified peptide/protein allows one to objectively monitor the expression and relative abundance of particular proteins from diverse samples, including tissue from transgenic mice of mixed genetic backgrounds. This robust bioinformatic approach also permits the comparison of proteomic data generated by different laboratories since it is instrument- and database-independent. Applying these statistical models to our initial studies, we detected a total of 117 oxidatively modified (carbonylated) proteins, 59 of which were specifically associated with PS1 + AbetaPP mice. Pathways and network component analyses suggest that there are three major protein networks that could be potentially altered in PS1 + AbetaPP mice as a result of oxidative modifications. These pathways are 1) iNOS-integrin signaling pathway, 2) CRE/CBP transcription regulation and 3) rab-lyst vesicular trafficking. We believe the results of these studies will help establish an initial AD database of oxidatively modified proteins and provide a foundation for the design of future hypothesis driven research in the areas of aging and neurodegeneration.

Beta-amyloid accumulation in APP mutant neurons reduces PSD-95 and GluR1 in synapses

Synaptic dysfunction is increasingly viewed as an early manifestation of Alzheimer's disease (AD), but the cellular mechanism by which beta-amyloid (Abeta) may affect synapses remains unclear. Since cultured neurons derived from APP mutant transgenic mice secrete elevated levels of Abeta and parallel the subcellular Abeta accumulation seen in vivo, we asked whether alterations in synapses occur in this setting. We report that cultured Tg2576 APP mutant neurons have selective alterations in pre- and post-synaptic compartments compared to wild-type neurons. Post-synaptic compartments appear fewer in number and smaller, while active pre-synaptic compartments appear fewer in number and enlarged. Among the earliest changes in synaptic composition in APP mutant neurons were reductions in PSD-95, a protein involved in recruiting and anchoring glutamate receptor subunits to the post-synaptic density. In agreement, we observed early reductions in surface expression of glutamate receptor subunit GluR1 in APP mutant neurons. We provide evidence that Abeta is specifically involved in these alterations in synaptic biology, since alterations in PSD-95 and GluR1 are blocked by gamma-secretase inhibition, and since exogenous addition of synthetic Abeta to wild-type neurons parallels changes in synaptic PSD-95 and GluR1 observed in APP mutant neurons.

Structural alterations at the neuromuscular junctions of matrix metalloproteinase 3 null mutant mice

Matrix metalloproteinases are important regulators of extracellular matrix molecules and cell-cell signaling. Antibodies to matrix metalloproteinase 3 (MMP3) recognize molecules at the frog neuromuscular junction, and MMP3 can remove agrin from synaptic basal lamina (VanSaun & Werle, 2000). To gain insight into the possible roles of MMP3 at the neuromuscular junction, detailed observations were made on the structure and function of the neuromuscular junctions in MMP3 null mutant mice. Striking differences were found in the appearance of the postsynaptic apparatus of MMP3 null mutant mice. Endplates had an increased volume of AChR stained regions within the endplate structure, leaving only small regions devoid of AChRs. Individual postsynaptic gutters were wider, containing prominent lines that represent the AChRs concentrated at the tops of the junctional folds. Electron microscopy revealed a dramatic increase in the number and size of the junctional folds, in addition to ectopically located junctional folds. Electrophysiological recordings revealed no change in quantal content or MEPP frequency, but there was an increase in MEPP rise time in a subset of endplates. No differences were observed in the rate or extent of developmental synapse elimination. In vitro cleavage experiments revealed that MMP3 directly cleaves agrin. Increased agrin immunofluorescence was observed at the neuromuscular junctions of MMP3 null mutant mice. These results provide strong evidence that MMP3 is involved in the control of synaptic structure at the neuromuscular junction and they support the hypothesis that MMP3 is involved in the regulation of agrin at the neuromuscular junction.

GABRD encoding a protein for extra- or peri-synaptic GABAA receptors is a susceptibility locus for generalized epilepsies

A major challenge in understanding complex idiopathic generalized epilepsies has been the characterization of their underlying molecular genetic basis. Here, we report that genetic variation within the GABRD gene, which encodes the GABAA receptor delta subunit, affects GABA current amplitude consistent with a model of polygenic susceptibility to epilepsy in humans. We have found a GABRD Glu177Ala variant which is heterozygously associated with generalized epilepsy with febrile seizures plus. We also report an Arg220His allele in GABRD which is present in the general population. Compared with wild-type receptors, alpha1beta2Sdelta GABAA receptors containing delta Glu177Ala or Arg220His have decreased GABAA receptor current amplitudes. As GABAA receptors mediate neuronal inhibition, the reduced receptor current associated with both variants is likely to be associated with increased neuronal excitability. Since delta subunit-containing receptors localize to extra- or peri-synaptic membranes and are thought to be involved in tonic inhibition, our results suggest that alteration of this process may contribute to the common generalized epilepsies.

Effects of congenital deafness in the cochlear nuclei of Shaker-2 mice: an ultrastructural analysis of synapse morphology in the endbulbs of Held

It is well established that manipulation of the sensory environment can significantly alter central auditory system development. For example, congenitally deaf white cats exhibit synaptic alterations in the cochlear nucleus distinct from age-matched, normal hearing controls. The large, axosomatic endings of auditory nerve fibers, called endbulbs of Held, display reduced size and branching, loss of synaptic vesicles, and a hypertrophy of the associated postsynaptic densities on the target spherical bushy cells. Such alterations, however, could arise from the cat's genetic syndrome rather than from deafness. In order to examine further the role of hearing on synapse development, we have studied endbulbs of Held in the shaker-2 ( sh2 ) mouse. These mice carry a point mutation on chromosome 11, affecting myosin 15 and producing abnormally short stereocilia in hair cells of the inner ear. The homozygous mutant mice are born deaf and develop perpetual circling behavior, although receptor cells and primary neurons remain intact at least for the initial 100 days of postnatal life. Endbulbs of Held in 7-month old, deaf sh2 mice exhibited fewer synaptic vesicles in the presynaptic ending, the loss of intercellular cisternae, and a hypertrophy of associated postsynaptic densities. On average, postsynaptic density area for sh2 endbulbs was 0.23 +/- 0.19 microm(2) compared to 0.07 +/- 0.04 microm(2) ( p < 0.001) for age-matched, hearing littermates. These changes at the endbulb synapse in sh2 mice resemble those of the congenitally deaf white cat and are consistent with the idea that they represent a generalized response to deafness.

Virus-induced neurobehavioral disorders: mechanisms and implications

One hypothesis for the etiology of neuropsychiatric disorders proposes that viral infection contributes to the induction of neuronal system dysfunction, resulting in a wide range of behavioral abnormalities. Recent research in molecular biology supports this hypothesis and refocuses on the role of viral infection in the development of psychiatric disorders. Viral infection can induce deleterious effects in the central nervous system by direct and/or indirect pathways. Understanding the mechanisms of glial cell dysfunction caused by persistent viral infection should lead to novel insights into the development of neurobehavioral disorders, including human mental illnesses, and to the possible development of treatments.

Electrophysiological and morphological characterization of a case of autosomal recessive congenital myasthenic syndrome with acetylcholine receptor deficiency due to a N88K rapsyn homozygous mutation

Congenital myasthenic syndromes are rare heterogeneous hereditary disorders, which lead to defective neuromuscular transmission resulting in fatigable muscle weakness. Post-synaptic congenital myasthenic syndromes are caused by acetylcholine receptor kinetic abnormalities or by acetylcholine receptor deficiency. Most of the congenital myasthenic syndromes with acetylcholine receptor deficiency are due to mutations in acetylcholine receptor subunit genes. Some have recently been attributed to mutations in the rapsyn gene. Here, we report the case of a 28-year-old French congenital myasthenic syndrome patient who had mild diplopia and fatigability from the age of 5 years. His muscle biopsy revealed a marked reduction in rapsyn and acetylcholine receptor at neuromuscular junctions together with a simplification of the subneural apparatus structure. In this patient, we excluded mutations in the acetylcholine receptor subunit genes and identified the homozygous N88K rapsyn mutation, which has already been shown by cell expression to impair rapsyn and acetylcholine receptor aggregation at the neuromuscular junction. The detection of the N88K mutation at the heterozygous state in five of 300 unrelated control subjects shows that this mutation is not infrequent in the healthy population. Electrophysiological measurements on biopsied intercostal muscle from this patient showed that his rapsyn mutation-induced fatigable weakness is expressed not only in a diminution in acetylcholine receptor membrane density but also in a decline of endplate potentials evoked at low frequency.

Synaptic pathology in Alzheimer's disease: a review of ultrastructural studies

Morphologic studies of the neuropathology in Alzheimer's disease (AD) have demonstrated significant loss of synaptic connectivity in many regions of the neocortex and hippocampus. The strongest correlation with cognitive decline in AD is with the synaptic density. This article discusses the ultrastructural studies that have documented changes in synaptic numbers in many areas of association cortex and in the hippocampal dentate gyrus molecular layer. Changes in the synaptic complex are discussed as a possible compensatory mechanism in response to synapse loss and a model is proposed to help relate the significance of these synaptic changes. Comparisons are made between results observed with ultrastructural technique and those utilizing immunohistochemistry to assess changes in synaptic pathology. Possible reasons underlying the synaptic neuropathology are discussed.

Rapsyn mutations in myasthenic syndrome due to impaired receptor clustering

Rapsyn, a 43-kDa postsynaptic protein, is essential for anchoring and clustering acetylcholine receptors (AChRs) at the endplate (EP). Mutations in the rapsyn gene have been found to cause a postsynaptic congenital myasthenic syndrome (CMS). We detected six patients with CMS due to mutations in the rapsyn gene (RAPSN). In vitro studies performed in the anconeus muscle biopsies of four patients showed severe reduction of miniature EP potential amplitudes. Electron microscopy revealed various degrees of impaired development of postsynaptic membrane folds. All patients carried the N88K mutation. Three patients were homozygous for N88K and had less severe phenotypes and milder histopathologic abnormalities than the three patients who were heterozygous and carried a second mutation (either L14P, 46insC, or Y269X). Surprisingly, two N88K homozygous patients had one asymptomatic relative each who carried the same genotype, suggesting that additional genetic factors to RAPSN mutations are required for disease expression.

Ultrastructural correlates of haloperidol-induced oral dyskinesias in rats: a study of unlabeled and enkephalin-labeled striatal terminals

Chronic neuroleptic treatment in rats induces vacuous chewing movements (VCMs) that mimic tardive dyskinesia. Such treatment decreases overall striatal synaptic density, but rats with VCMs also have decreased density of symmetric synapses, indicating less inhibitory synaptic transmission. This study examined the striatum to determine if enkephalinergic terminals, which form symmetric synapses, are affected. All synapses combined, asymmetric and symmetric axospinous, and enkephalinergic synapses were significantly reduced in density in the haloperidol treated group as compared to controls. A loss of asymmetric axodendritic synapses, typical of excitatory thalamic inputs, was observed preferentially in the low VCM group. A loss of symmetric axodendritic synapses was observed preferentially in the high VCM group. This study indicates that a population of synapses, other than enkephalinergic ones, is preferentially lost in the high VCM group. Moreover, lack of VCMs may be due to changes in synaptic organization that are protective as well as the absence of pathologic connections.

Synapse formation is regulated by the signaling adaptor GIT1

Dendritic spines in the central nervous system undergo rapid actin-based shape changes, making actin regulators potential modulators of spine morphology and synapse formation. Although several potential regulators and effectors for actin organization have been identified, the mechanisms by which these molecules assemble and localize are not understood. Here we show that the G protein-coupled receptor kinase-interacting protein (GIT)1 serves such a function by targeting actin regulators and locally modulating Rac activity at synapses. In cultured hippocampal neurons, GIT1 is enriched in both pre- and postsynaptic terminals and targeted to these sites by a novel domain. Disruption of the synaptic localization of GIT1 by a dominant-negative mutant results in numerous dendritic protrusions and a significant decrease in the number of synapses and normal mushroom-shaped spines. The phenotype results from mislocalized GIT1 and its binding partner PIX, an exchange factor for Rac. In addition, constitutively active Rac shows a phenotype similar to the GIT1 mutant, whereas dominant-negative Rac inhibits the dendritic protrusion formation induced by mislocalized GIT1. These results demonstrate a novel function for GIT1 as a key regulator of spine morphology and synapse formation and point to a potential mechanism by which mutations in Rho family signaling leads to decreased neuronal connectivity and cognitive defects in nonsyndromic mental retardation.

Synaptic reorganization of calbindin-positive neurons in the human hippocampal CA1 region in temporal lobe epilepsy

The distribution, morphology, synaptic coverage and postsynaptic targets of calbindin-containing interneurons and afferent pathways have been analyzed in the control and epileptic CA1 region of the human hippocampus. Numerous calbindin-positive interneurons are preserved even in the strongly sclerotic CA1 region. The morphology of individual cells is altered: the cell body and dendrites become spiny, the radially oriented dendrites disappear, and are replaced by a large number of curved, distorted dendrites. Even in the non-sclerotic epileptic samples, where pyramidal cells are present and calbindin-immunoreactive interneurons seem to be unchanged, some modifications could be observed at the electron microscopic level: they received more inhibitory synaptic input, and the calbindin-positive excitatory afferents - presumably derived from the CA1, the CA2 and/or the dentate gyrus - are sprouted. In the strongly sclerotic tissue, with the death of pyramidal cells, calbindin-positive terminals (belonging to interneurons and the remaining excitatory afferents) change their targets. Our data suggest that an intense synaptic reorganization takes place in the epileptic CA1 region, even in the non-sclerotic tissue, before the death of considerable numbers of pyramidal cells. Calbindin-positive interneurons participate in this reorganization: they show plastic changes in response to epilepsy. The enhanced inhibition of inhibitory interneurons may result in the disinhibition of pyramidal cells or in an abnormal synchrony in the output region of the hippocampus.

Levodopa but not ropinirole induces an internalization of D1 dopamine receptors in parkinsonian rats

Levodopa therapy in Parkinson's disease is mediated by dopamine receptors and, in a recent study, we showed that a Dl full agonist can induce an internalization of D1 dopamine receptors. The aim of the present study was to determine whether levodopa or a dopamine agonist such as ropinirole can also induce the internalization of D1 dopamine receptors in the striatum of control and hemiparkinsonian rats. The distribution of D1 dopamine receptors was analyzed by immunohistochemistry using a specific antibody. In control animals and 6-hydroxydopamine (6-OHDA)-lesioned animals treated with saline, D1 dopamine receptors were localized at the level of the plasma membrane. In contrast, in both lesioned and nonlesioned animals receiving a single dose of levodopa, but not in animals receiving ropinirole, D1 dopamine receptors were internalized in the cytoplasm. This result is likely explained by the fact that ropinirole binds to non-D1 dopamine receptors, whereas levodopa, which increases dopamine levels, indirectly acts on both D1 and D2 receptors. Ropinirole is consequently less likely to desensitize D1 dopamine receptors than levodopa and, thus, to reduce the efficacy of the treatment.

Synaptic localization of GABA(A) receptor subunits in the substantia nigra of the rat: effects of quinolinic acid lesions of the striatum

The inhibitory amino acid, gamma-aminobutyric acid (GABA), plays a critical role in the substantia nigra (SN) in health and disease. GABA transmission is controlled in part by the type(s) of GABA receptor expressed, their subunit composition and their location in relation to GABA release sites. In order to define the subcellular localization of GABA(A) receptors in the SN in normal and pathological conditions, sections of SN from control rats and rats that had received quinolinic acid lesions of the striatum were immunolabelled using the postembedding immunogold technique with antibodies against subunits of the GABA(A) receptor. Immunolabelling for alpha1, beta2/3 and gamma2 subunits was primarily located at symmetrical synapses. Double-labelling revealed that beta2/3 subunit-positive synapses were formed by terminals that were enriched in GABA. Colocalization of alpha1, beta2/3 and gamma2 subunits occurred at individual symmetrical synapses, some of which were identified as degenerating terminals derived from the striatum. In the SN ipsilateral to the striatal lesion there was a significant elevation of immunolabelling for beta2/3 subunits of the GABA(A) receptor at symmetrical synapses, but not of GluR2/3 subunits of the AMPA receptor at asymmetrical synapses. It was concluded that fast GABA(A)-mediated transmission occurs primarily at symmetrical synapses within the SN, that different receptor subunits coexist at individual synapses and that the upregulation of GABA(A) receptors following striatal lesions is expressed as increased receptor density at synapses. The upregulation of GABA(A) receptors in Huntington's disease and its models is thus likely to lead to an increased efficiency of transmission at intact GABAergic synapses in the SN and may partly underlie the motor abnormalities of this disorder.

[(3)H]cAMP binding sites and protein kinase a activity in the prefrontal cortex of suicide victims

OBJECTIVE

The cAMP-dependent enzyme protein kinase A phosphorylates intracellular proteins upon activation and thereby plays a major role in mediating various physiological functions in the brain. To examine the role of this enzyme in suicidal behavior, the authors examined the catalytic and regulatory activities of protein kinase A in the postmortem brain of suicide victims.

METHOD

Brain tissues were collected from 17 suicide victims and 17 nonpsychiatric comparison subjects. Regulatory activity was determined by examining [(3)H]cAMP binding to protein kinase A, while catalytic activity was determined by enzymatic assay in the presence (total activity) and the absence (endogenous activity) of cAMP in the membrane and cytosol fractions of the prefrontal cortex.

RESULTS

The number (B(max)) of [(3)H]cAMP binding sites to protein kinase A was significantly lower in the suicide victims without any changes in affinity in either the membrane or cytosol fractions of the prefrontal cortex. Further, significantly less protein kinase A activity, both in the presence and the absence of cAMP, was seen in the membrane and cytosol fractions of the prefrontal cortex of suicide victims; however, the difference in total protein kinase A activity was much more pronounced.

CONCLUSIONS

The results suggest that cAMP binding to the regulatory subunits of protein kinase A, as well as the phosphotransfer catalytic activity of protein kinase A, are lower in the prefrontal cortex of suicide victims than in nonpsychiatric comparison subjects, which may be of clinical relevance in the pathophysiology of suicidal behavior.

DrosophilaAmphiphysin is implicated in protein localization and membrane morphogenesis but not in synaptic vesicle endocytosis

Amphiphysin family members are implicated in synaptic vesicle endocytosis, actin localization and one isoform is an autoantigen in neurological autoimmune disorder; however, there has been no genetic analysis of Amphiphysin function in higher eukaryotes. We show that Drosophila Amphiphysin is localized to actin-rich membrane domains in many cell types, including apical epithelial membranes, the intricately folded apical rhabdomere membranes of photoreceptor neurons and the postsynaptic density of glutamatergic neuromuscular junctions. Flies that lack all Amphiphysin function are viable, lack any observable endocytic defects, but have abnormal localization of the postsynaptic proteins Discs large, Lethal giant larvae and Scribble, altered synaptic physiology, and behavioral defects. Misexpression of Amphiphysin outside its normal membrane domain in photoreceptor neurons results in striking morphological defects. The strong misexpression phenotype coupled with the mild mutant and lack of phenotypes suggests that Amphiphysin acts redundantly with other proteins to organize specialized membrane domains within a diverse array of cell types.

Reduced NAA in the thalamus and altered membrane and glial metabolism in schizophrenic patients detected by 1H-MRS and tissue segmentation

Functional and structural abnormalities in the thalamus as well as a generalized phospholipid membrane disorder have been implicated in the pathogenesis of schizophrenic psychosis. To determine whether thalamic neuronal abnormalities and altered membrane-associated metabolites can be detected in schizophrenic patients, we used in vivo proton magnetic resonance spectroscopy (1H-MRS) in 32 acutely-ill, medicated schizophrenic patients and 17 age-matched controls. Thalamic and white matter metabolite concentrations (myo-inositol (mI), choline-containing compounds (Cho), total creatine (Cr) and N-acetylaspartate (NAA)) were estimated and corrected for atrophy (CSF) and gray and white matter contributions (GM, WM) by use of image-based voxel segmentation. Thalamic NAA was significantly reduced in schizophrenic patients, whereas Cho and mI were significantly increased in the parietal white matter. White matter Cr was significantly elevated in patients and correlated positively with the brief psychiatric rating scores (BPRS). Regional metabolite levels were inversely associated with GM and WM content reaching significance for mI and Cr in the thalamus and Cho and NAA in the white matter. Reduced NAA in the left thalamus of schizophrenic patients confirms and extends previous spectroscopic data and agrees well with histologic and imaging findings of reduced neuronal density and volume. Elevated Cho in line with 31P-MRS studies suggests increased myelin degradation thus further supporting a generalized membrane disorder in schizophrenic patients. In addition, we demonstrate the need to correct metabolite concentrations for regional tissue composition in studies employing patients with altered brain morphology.

Abnormalities in the synaptic vesicle fusion machinery in Huntington's disease

We have recently described the progressive and selective loss of the presynaptic protein complexin II in brains of mice (R6/2) transgenic for the Huntington's disease (HD) mutation. Here we have determined the expression of components of the synaptic vesicle fusion machinery in the striatum and hippocampus from post-mortem brains of HD cases and neurologically normal controls. As in the brains of R6/2 mice, complexin II was markedly depleted in the HD striatum; the depletion was compartmentally organized, with complexin II-poor regions corresponding with areas of low immunoreactivity toward the matrix marker calbindin D(28K). Decreases in the levels of the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) protein synaptobrevin 2 and of rab3A were also seen, but none of the other proteins tested was significantly affected. In the hippocampus, levels of complexin II, synaptobrevin 2, rab3A, and also of alpha-SNAP, were markedly elevated in HD brains. We suggest that the observed abnormalities in the expression of proteins known to be involved in the control of neurotransmitter release, including both modulators and core components of the vesicle fusion machinery, might account for at least some of the functional abnormalities seen in HD.

Miller Fisher syndrome: immunofluorescence and immunoelectron microscopic localization of IgG at the mouse neuromuscular junction

In vitro electrophysiological experiments have demonstrated that IgG antibodies from patients with Miller Fisher syndrome (MFS) impair neuromuscular transmission by a fast and completely reversible combined pre- and postsynaptic blockade. In this study we investigated the cellular and subcellular binding sites of IgG from four MFS patients at the mouse hemidiaphragm by immunofluorescence and immunoelectron microscopy. IgG from all patients produced significant immunostaining at the neuromuscular junction, whereas sera from healthy volunteers or from patients with other neurological diseases did not stain neuromuscular junction. Immunoelectron microscopy revealed that, when living hemidiaphragms were incubated with IgG from MFS patients, labeling was found on both pre- and postsynaptic membranes of the neuromuscular junction, whereas terminal Schwann cells and the basal lamina covering the synaptic membranes were not labeled. These findings demonstrate that IgG from MFS patients binds to synaptic membranes of the neuromuscular junction where it might interfere with the function of both the pre- and postsynaptic activities.

Serotonin(2A) receptors are reduced in the planum temporale from subjects with schizophrenia

[(3)H]ketanserin binding to 5HT(2A) receptors was measured in the left planum temporale (sensory speech cortex) from schizophrenic and non-schizophrenic (control) subjects using both particulate membranes and tissue sections. There was a significant decrease in the affinity of [(3)H]ketanserin binding to particulate membranes from schizophrenic subjects who were treated with phenothiazines up to death. Adding 2nM chlorpromazine to brain tissue from control subjects caused a similar decrease in the affinity of [(3)H]ketanserin binding to particulate membranes. This suggests that the decrease in affinity observed in the phenothiazine-treated subjects was due to residual drugs. In addition, there was a significant decrease in the density of [(3)H]ketanserin binding in both particulate membranes and tissue sections from schizophrenic subjects which did not appear to be due to residual antipsychotic drugs. Analysis of the laminar distribution of 5HT(2A) receptors showed that this decrease was greatest in cortical layer III. The decrease in the density of 5HT(2A) receptors was significant whether schizophrenic subjects were receiving phenothiazines or haloperidol at the time of death, and there was no correlation between the last recorded dose of antipsychotic drug and 5HT(2A) receptor density. These data suggest that a decrease in the density of 5HT(2A) receptors in the planum temporale may be associated with the pathology of schizophrenia.

[Histological structure of adult mouse brain in protein-deficient nutrition]

The effect of protein deficient nutrition on histostructure of different regions of brain of mature animals was studied in the experimental model of protein and energy deficiency. Protein deficient nutrition was shown to exert negative influence on structural and functional state of brain neurons which is manifested through increase of dystrophic changes in neurons of all brain regions, accumulation of lipofuscine in neurons and complex of structural changes in synaptic contacts.

In vivo modulation of rodent glutathione and its role in peroxynitrite-induced neocortical synaptosomal membrane protein damage

Peroxynitrite, formed by the reaction between nitric oxide and superoxide, leads to the oxidation of proteins, lipids, and DNA, and nitrates thiols such as cysteine and glutathione, and amino acids like tyrosine. Previous in vitro studies have shown glutathione to be an efficient scavenger of peroxynitrite, protecting synaptosomal membranes from protein oxidation, the enzyme glutamine synthetase from inactivation, and preventing the death of hippocampal neurons in culture. The current study was undertaken to see if in vivo modulation of glutathione levels would affect brain cortical synaptosomal membrane proteins and their subsequent reaction with peroxynitrite. Glutathione levels were depleted, in vivo, by injecting animals with 2-cyclohexen-1-one (CHX, 100 mg/kg body weight), and levels of glutathione were enhanced by injecting animals with N-acetylcysteine (NAC, 200 mg/kg body weight), which gets metabolized to cysteine, a precursor of glutathione. Changes in membrane protein conformation and structure in synaptosomes subsequently isolated from these animals were examined using electron paramagnetic resonance, before and after in vitro addition of peroxynitrite. The animals injected with the glutathione depletant CHX showed greater damage to the membrane proteins both before and after peroxynitrite treatment, compared to the non-injected controls. The membrane proteins from animals injected with NAC were comparable to controls before peroxynitrite treatment and were partially protected against peroxynitrite-induced damage. This study showed that modulation of endogenous glutathione levels can affect the degree of peroxynitrite-induced brain membrane damage and may have potential therapeutic significance for oxidative stress-associated neurodegenerative disorders.

A unique familial leukodystrophy with adult onset dementia and abnormal glycolipid storage: a new lysosomal disease?

Two adult siblings with early onset dementia are described. At presentation, in their early 30s, they showed poor judgment and disinhibition. A progressive dementia ensued over several years. Brain MRI disclosed diffusely increased T2 signal in the cerebral white matter, suggestive of a leukodystrophy. Numerous lysosomal enzyme assays including leucocyte arylsulphatase A and galactocerebrosidase activities, plasma and fibroblast very long chain fatty acid concentrations, and urinary sulphatide concentrations were normal, as were CSF analyses. A brain biopsy disclosed periodic acid Schiff (PAS) and Sudan black positive material in perivascular macrophages which, by electron microscopy, consisted of stacks of straight or curvilinear paired membranes within angulate lysosomes, indicative of abnormal glycolipid accumulation. The combination of clinical, radiological, biochemical, and pathological features of this degenerative disease is not consistent with that of any of the known leukodystrophies or lysosomal storage disorders. These findings suggest a previously undescribed familial glycolipid storage disorder causing an adult onset leukodystrophy and presenting with behavioural symptoms that mimic a psychiatric disorder.

Reduced immunoreactivity of type I adenylyl cyclase in the postmortem brains of alcoholics

Reduced adenylyl cyclase activity after chronic ethanol exposure has been reported. In this study, we investigated by immunoblotting whether quantitative changes of adenylyl cyclase isoforms (type I, type II, and type V/VI adenylyl cyclases) exist in membrane preparations of the temporal cortex obtained from six alcoholics and six age-matched controls. The immunoreactivity of type I adenylyl cyclase decreased significantly in the temporal cortex of alcoholics when compared with controls (p < 0.05), whereas those of type II and type V/VI adenylyl cyclases showed no changes between the groups. These findings suggest that these isoform-specific afterations in the adenylyl cyclase system may be involved in the pathophysiology of alcoholism.

Differential alteration of adenylyl cyclase subtypes I, II, and V/VI in postmortem human brains of heroin addicts

In animal and culture cell experiments, the upregulation of cAMP-related signal transduction after chronic opioid administration has been hypothesized to be an adaptive change of the molecular mechanism to maintain homeostasis in intracellular signals downstream from opioid receptors. Herein, we have examined the quantitative changes of three adenylyl cyclase (AC) subtypes (I, II, and V/VI) in temporal cortex membranes from brains of heroin addicts and age-matched controls by immunoblotting. The immunoreactivity of AC-I decreased significantly (p < 0.05) in heroin addicts, compared with controls; whereas those of AC-II and AC-V/VI were not changed. The present findings indicate that differential regulation of AC subtypes occurs and that AC-I may play an important role in the signal transduction for opiate-induced tolerance and dependence mechanisms in human brain cortex.

Membrane components separate early-onset Alzheimer's disease from senile dementia of the Alzheimer type

Brain tissue from 12 subjects with pure Alzheimer's disease (AD) and 21 subjects with senile dementia of the Alzheimer type (SDAT) was investigated for membrane lipids and compared with that in age-matched controls. In brain tissue from the patients with AD, phospholipids were significantly decreased compared with that from SDAT patients and controls, cholesterol was reduced compared with that in controls, and gangliosides were significantly reduced in all gray-matter areas investigated compared with those in both SDAT subjects and controls. A reduction in gangliosides also occurred in the SDAT group, but it was smaller. In the white matter, the pattern of changes was the opposite. Phospholipids, cholesterol, cerebroside, and sulfatide were significantly reduced in the frontal-lobe white matter in the SDAT group compared with that in age-matched controls and AD patients. Gangliosides in the cerebrospinal fluid also separated AD from SDAT and controls. The findings indicate synapse degeneration as an important pathogenetic factor in AD. This disorder should be separated from SDAT, in which white-matter degeneration appears to be more prominent.

The superimposed effects of chronic phrenicotomy and cervical spinal cord hemisection on glial cytoarchitecture in the rat phrenic nucleus

This study was conducted to determine the effects of chronic phrenicotomy on spinal hemisection-induced morphological plasticity occurring in the phrenic nucleus. Young adult rats were divided into a hemisection-alone and two hemisection-plus-phrenicotomy (HPP) groups. HPP animals received a left phrenicotomy two or four weeks prior to sacrificing; whereas hemisection-alone animals did not. All animals received a left C2 spinal hemisection 24 hours prior to death. Quantitative morphometric analysis of the phrenic nucleus showed significant reductions in phrenic dendritic size and the number of dendrodendritic appositions in HPP (two week) animals and in the length of dendrodendritic appositions in HPP (four week) animals. Significant increases in microglial area fraction in HPP (two week) animals and in astroglia area fraction in HPP (four week) animals were also detected. The results suggest that the alterations in the spinal hemisection-induced dendrodendritic apposition formation is most likely influenced by the different stages of the glial reactions induced by the chronic phrenicotomy/spinal hemisection.

A chronic physiological rat model of dementia

We have developed an aging rat model that mimics specific pathology reported in dementia, particularly Alzheimer's disease (AD). The model involves subjecting rats to chronic cerebrovascular insufficiency (CVI) for 1-9 weeks. Gross and sensory-motor function remains normal but spatial memory acquisition and retention are impaired after 1 week and worsens progressively with time. In vivo [31P]NMR spectroscopy evaluation in CVI animals showed membrane phospholipid synthesis increase in the hippocampal-cortex region of affected animals which increases with time. Post-mortem examination revealed that CA1 neurons can express selective damage 1 week after CVI and the number of CA1 neurons thus affected increases in proportion with time. MOreover, there is progressive increase in GFAP hypertrophy and hyperplasia in the hippocampal region during the 9-week observation period. Reduction of microtubule-associated protein 2 and pre-terminal noradrenergic varicosities in the hippocampus-cortex is seen after 9 weeks but not 1 week of CVI. All the above changes have been reported in AD-affected brains. The present CVI model appears as a useful screen in investigating potential therapy for AD as well as increasing understanding of this disorder.

Cochlear synaptic development and morphology in a genetically induced type of progressive hair cell degeneration

In mice with genetically induced inner ear abnormalities it is conceivable that in the morphogenetic types and in mutants with the spotting kind of pigmentary anomaly, the genes act through the developing nervous system. It has been suggested that in degenerative (neuroepithelial) mutants the influence of the gene is also reflected in the inner ear through the agency of the nervous system. The jerker mouse belongs to the neuroepithelial type of mutants which in homozygotes results in early postnatal degeneration of the sensory epithelium of the inner ear, initially confined to the cuticular plate and the stereocilia. In spite of well-advanced hair cell degeneration, these mutants developed morphologically normal afferent and efferent nerve terminals at cochlear hair cells.

Cerebral cortex beta-adrenoceptor binding in bipolar affective disorder

Beta-Adrenoceptor density was measured in cerebral cortex membranes obtained postmortem from age-matched controls and subjects with bipolar disorder (BD). [125I]Iodopindolol (PIN) binding performed using a single point concentration was not different in frontal, occipital or temporal cortex in BD. Scatchard analysis of [125I]PIN binding in temporal cortex confirmed the lack of differences in binding density and no changes in KD between these two subject groups. These findings do not support alterations in the density or affinity of beta-adrenoceptor binding in cerebral cortex in BD.

Programs for visualization in three-dimensional microscopy

Three-dimensional data representing biological structures can be derived using several methods, including serial section reconstruction, optical sectioning, and tomography. The investigation, comprehension, and communication of structural relationships to others is greatly facilitated by computer-based visualization procedures. We describe SYNU, a suite of programs developed for interactive investigation of three-dimensional structure and for the production of high-quality three-dimensional images and animations. We illustrate the capabilities of SYNU in applications to biological data obtained by confocal light microscopy, serial section, and high-resolution electron microscopy from investigations at the cellular, subcellular, and molecular levels.