beta-APP cognitive function versus beta-amyloid--induced cell death

The beta-amyloid precursor protein (beta-APP) has been hypothesized to play an important role in the establishment of synaptic connections. Icv injections of anti-beta APP antibodies into rat brains produced no appreciable effect on subsequent learning of a passive avoidance task whereas memory assessed 1 day later in a retention test was impaired in anti-beta-APP--but not control-IgG-injected animals. This suggests a possible involvement of beta-APPs in cognitive functions. In order to evaluate the properties of the proteolytic A beta-fragment accumulating in Alzheimer's disease brains, four different neuronal cell types were exposed to A beta 1-42 for 24 hours. All cells degenerated in response to A beta, yet chromosomal condensation and internucleosomal DNA fragmentation, typical for apoptosis, occurred in only three of the cell types tested. These findings suggest that beta-APPs may play an important role in cognitive processes and additionally, that their alternative proteolytic product A beta may be differentially toxic to neuronal cell types, inducing cell death either by necrosis or by apoptosis.

The sensitive individual and the indoor environment: case study

This case study describes an indoor environment investigation initiated in response to numerous health and comfort complaints suspected of being associated with a two-story office building. Conventional indoor environment investigation techniques were applied in an attempt to identify one or several contributing factors, such as inadequate outdoor air ventilation and the presence of a respiratory irritant. The air quality satisfaction percentage in the building was well above 80%; however, at least one individual was experiencing a fairly severe reaction only upon entering the subject building. Evaluating the building indoor conditions as acceptable without attempting to address all possible building-related causes and communicating findings to interested occupants would likely have resulted in more occupant complaints and increased the potential for hysteria conditions. This investigation necessarily addressed a sensitive individual and involved an occupational physician as a constructive participant in the investigation.

Comparison of benzodiazepine receptor ligands with partial agonistic, antagonistic or partial inverse agonistic properties in precipitating withdrawal in squirrel monkeys

Benzodiazepine receptor (BZR) ligands previously characterized as differing in intrinsic efficacy were evaluated first for potency in antagonizing flunitrazepam-induced sleep in monkeys. Data from these experiments were used to define approximately equieffective doses for subsequent use in precipitating withdrawal in diazepam-treated monkeys. It was shown that partial agonists with intermediate intrinsic efficacy (bretazenil, Ro 41-7812) were relatively ineffective in precipitating withdrawal reactions in diazepam-treated squirrel monkeys. The potent and specific BZR antagonist flumazenil, which possesses weak intrinsic efficacy, was more effective in precipitating a withdrawal reaction in diazepam-treated monkeys. In contrast, the highest dose of the BZR antagonist ZK 93426 that could be administered failed to precipitate withdrawal under the same experimental conditions. Finally, the BZR partial inverse agonist sarmazenil was the most effective of these BZR ligands in eliciting a precipitated withdrawal reaction. Thus, the results of the present investigation strongly suggest that BZR ligands differing in intrinsic efficacy differentially precipitate withdrawal in squirrel monkeys treated chronically with diazepam.

Targeting and gene expression in spinal cord motor neurons following intramuscular inoculation of an HSV-1 vector

One problem in devising strategies of gene transfer to the nervous system is targeting specific neuronal populations. To evaluate the potential for using herpes simplex virus (HSV) as a vector for gene transfer to spinal cord motor neurons, the HSV-1 mutant LAT-LTR in which the E. coli beta-galactosidase gene is expressed under control of the HSV LAT core promoter (LAT) and the Moloney murine leukemia virus long terminal repeat (LTR) was inoculated unilaterally into the gastrocnemius muscle. Infectious virus was isolated from the spinal cord on days 3-7 post inoculation (PI). Immunocytochemical labeling of HSV antigen was detected in ipsilateral ventral horn neurons in the spinal cord at day 3 PI and had spread to contiguous spinal cord regions by day 6 PI. No viral antigen was detected at 14 or 28 DPI. beta-galactosidase expression (driven by the LAT-LTR promoter) was detected in neurons of the ventral horn on days 3, 6, 14, and 28 PI. Histological analysis showed mild lesions in the ventral horn on day 3 PI which progressed through days 6, 14 and 28 PI. This study demonstrates the feasibility of gene delivery into spinal motor neurons after injection of an HSV vector at a peripheral muscular site. This approach should prove useful in neurobiological investigations and it suggests a possible application to development of gene therapy for heritable diseases affecting motor neurons.

Dorsal periaqueductal gray-induced aversion as a simulation of panic anxiety: elements of face and predictive validity

Neurosurgical stimulation of the dorsal periaqueductal gray (dPAG) matter in man induces acute signs of autonomic arousal and feelings of subjective anxiety; those signs have phenomenological similarity with the symptom profile characterizing a panic attack. Animals undergoing dPAG stimulation show comparable physical signs of autonomic activation and sudden fear-suggestive behavioral reactions that can be shaped into operant self-interruption behavior. Drugs known to acutely reduce (alprazolam, clonazepam) or precipitate (yohimbine, caffeine) panic attacks in patients were found to acutely and dose-dependently reduce or enhance, respectively, aversion induced by dPAG stimulation in rats. When considered as an animal model of panic anxiety, the dPAG model simultaneously meets criteria of face validity (symptomatic homology) and predictive validity (pharmacological homology under short-term treatment); aspects of its construct validity (theoretical rationale supporting the model) are discussed. It is suggested that dPAG stimulation-induced aversion may represent a model of some aspects of panic disorders.

Familial hypertryptophanemia in two siblings

Mild and moderate mental retardation with exaggerated affective responses, periodic mood swings, and apparent hypersexual behavior were present in two siblings with hypertryptophanemia and tryptophanuria. In addition, the male had severe myopia, a speech impediment, musculoskeletal abnormalities and perceptual hypersensitivity. His sister was deaf, which was ascribed to antenatal rubella. The occurrence in siblings and the presence of abnormal urinary tryptophan metabolite in the mother and a half-sibling suggest that the condition results from an autosomal recessive gene with minor expression in some heterozygotes.

Precipitated withdrawal in squirrel monkeys after repeated daily oral administration of alprazolam, diazepam, flunitrazepam or oxazepam

The lowest dose of alprazolam, diazepam, flunitrazepam and oxazepam consistently to induce loss of righting reflex in squirrel monkeys or vehicle was orally administered to monkeys on 18 consecutive days: 2 mg/kg alprazolam (n = 4), 30 mg/kg diazepam (n = 4), 1 mg/kg flunitrazepam (n = 4), 280 mg/kg oxazepam (n = 5), or vehicle (n = 4). Tolerance developed rapidly for loss of righting reflex, more slowly for sleep and only minimally for muscle relaxation observed during the period immediately following daily oral administration. Injection of the specific benzodiazepine receptor antagonist flumazenil (10 mg/kg i.v.) 5 h after the ninth daily oral treatment produced signs of precipitated withdrawal (tremor, vomiting and/or convulsions) in one alprazolam-, four diazepam-, one flunitrazepam- and four oxazepam-treated monkeys, but not in the vehicle-treated monkeys. Physiological saline injected intravenously several days later under these same experimental conditions failed to provoke a precipitated withdrawal reaction. When flumazenil-induced precipitated withdrawal was again evaluated after the 18th daily oral treatment, withdrawal signs were observed in all alprazolam- and all diazepam-treated monkeys, as well as in three flunitrazepam- and three oxazepam-treated monkeys, but not in the vehicle-treated monkeys (convulsions were observed in one alprazolam-, two diazepam-, one flunitrazepam- and two oxazepam-treated monkeys). No signs of spontaneous withdrawal were observed in any of the monkeys during a subsequent 3-week drug-free period. Thus, repeated administration of approximately equieffective doses of these four benzodiazepines resulted in a similar development of tolerance and physical dependence (indicated by the occurrence of a precipitated withdrawal reaction).

The three-dimensional solution structure of human stefin A

The three-dimensional solution structure of recombinant human stefin A has been determined by a simulated annealing protocol using a total of 1113 distance and angle constraints obtained from 1H and 15N HMR spectroscopy. The solution structure is represented by a family of 17 conformers with an average root-mean-square deviation relative to the mean structure of 0.44 A for backbone atoms and 0.94 A for all heavy atoms for the main body of the structure. The protein has a well-defined global fold consisting of five anti-parallel beta-strands wrapped around a central five-turn alpha-helix. There is considerable similarity between the structural features of free stefin A in solution and the X-ray structure of the homologous protein stefin B in its complex with papain, but there are also some important differences in the regions which are fundamental to proteinase binding. The differences consist primarily of two regions of high conformational heterogeneity in free stefin A which correspond in stefin B to two of the components of the tripartite wedge that docks into the active site of the target proteinase. These regions, which are shown to be mobile in solution, are the five N-terminal residues and the second binding loop. In the bound conformation of stefin B they form a turn and a short helix, respectively.

Aniracetam reverses memory impairment in rats

The pyrrolidinone derivative aniracetam given orally immediately after acquisition of an inhibitory avoidance response reproducibly ameliorated scopolamine-induced amnesia in female rats in an extensive series of test sessions conducted over a 1-year period. In a dose-response experiment it was demonstrated that 50 mg kg-1 was the lowest oral dose of aniracetam to significantly ameliorate scopolamine-induced amnesia. Combined results from these numerous test sessions demonstrated that 50 mg kg-1 aniracetam administered to scopolamine-treated rats resulted in 53% of the animals exhibiting correct passive avoidance responding in the retention evaluation versus 9% of the scopolamine-treated rats given vehicle (in comparison, 64% of the rats injected with vehicle rather than scopolamine in this experimental situation exhibited correct responding in the retention test). There was minimal variation in this pattern of results over the successive 1-month blocks constituting the complete experimental period. Thus, the nootropic compound aniracetam replicably exhibited memory enhancing effects in this animal model of reduced cholinergic function.

Structural characterisation of human stefin A in solution and implications for binding to cysteine proteinases

Stefin A is a member of the cystatin superfamily of proteins which are tight and reversibly binding inhibitors of the papain-like cysteine proteinases. The 1H-NMR and 15N-NMR resonances of human stefin A have been sequentially assigned using two-dimensional homonuclear and heteronuclear NMR techniques in conjunction with three-dimensional heteronuclear methods. Characteristic sequential and medium range NOE contacts, J constants and hydrogen exchange data have been used to identify the secondary structural elements of the protein which consists of five anti-parallel beta-strands and a single alpha-helix. There is much similarity between the secondary structural features of stefin A and the homologous protein stefin B in its complex with papain [Stubbs, M. T., Laber, B., Bode, W., Huber, R., Jerala, R., Lenarcic, B. & Turk, V. (1990) EMBO. J. 9. 1939-1947] but also some important differences in regions which are fundamental to the binding event. The principal difference is the presence of two conformationally unrestricted regions in stefin A that form two of the components of the tripartite wedge which docks into the active site of the target proteinase. Specifically, these regions are the five N-terminal residues and the second binding loop, which form a turn and a short helix respectively, in the bound conformation of stefin B.

In situ PCR localization of herpes simplex virus DNA sequences in disseminated neonatal herpes encephalitis

To more precisely define the role of herpes simplex virus (HSV) in development of nervous system disease in neonates with disseminated infection, an in situ polymerase chain reaction (ISPCR) method was used to detect and localize HSV DNA sequences in paraffin sections of neural and non-neural autopsy tissues. In subregions of adjacent sections corresponding to ISPCR-labeled and unlabeled areas, HSV specificity was verified using solution PCR and Southern blots. In serial sections, ISPCR results were compared to lesions, HSV antigen and, in selected samples, to viral sequence detection by in situ hybridization. By ISPCR, HSV-specific labeling was limited to HSV-infected neonates and experimentally infected mouse controls. ISPCR-labeled cells corresponded to regions that were histologically abnormal and contained HSV antigen or in situ hybridization signal in some foci; in others, labeled cells were in areas with no evident lesions or antigen. Results suggest two routes of HSV spread to the CNS: (i) blood-borne infection, with HSV DNA in splenic lymphocytes, circulating cells, meningeal vessel walls and cells in intraventricular hemorrhage, and (ii) neural spread, with HSV detected in brain stem sensory neurons. In the brain of one neonate surviving acute infection, detection of HSV nucleic acid sequences suggests a latent or persistent viral genome. With other methods, this highly sensitive ISPCR technique permits a more complete definition of HSV infection in these infants and provides new insights into disease mechanisms. Fuller understanding of HSV persistence and recurrent neurological disease in survivors will require further studies using these and other techniques in human tissues and in animal models.

Investigating the genetic basis for ankylosing spondylitis. Linkage studies with the major histocompatibility complex region

OBJECTIVE

To assess the hypothesis that B27 or a gene(s) in close proximity (e.g., within or near the major histocompatibility complex [MHC]) represents a disease-causing ankylosing spondylitis (AS) gene, and therefore contributes directly to the pathogenesis of this disorder.

METHODS

MHC haplotypes were determined by both serologic and molecular analyses in 15 multiple-case AS families from Toronto and Newfoundland. Segregation of MHC haplotypes with AS within these families was examined by linkage and identity-by-descent analyses. Attributable risk estimates for various genetic markers and for sex were calculated.

RESULTS

Linkage analyses established significant linkage between AS and the MHC, the maximal logarithm of odds (LOD) score being 3.48 at a recombination frequency (O) of 0.05. In a second analysis in which the population association of the MHC gene HLA-B27 with AS was taken into account, the maximal LOD score was 7.5 at O = 0.05. Identity-by-descent analyses showed a significant departure from random segregation among affected avuncular (P < 0.05) and cousin (P < 0.01) pairs. The presence of HLA-B40 in HLA-B27 positive individuals increased the risk for disease more than 3-fold, confirming previous reports. Disease susceptibility modeling suggested an autosomal dominant pattern of inheritance, with penetrance of approximately 20%.

CONCLUSION

These data provide the first conclusive demonstration of linkage between the MHC region and AS, and confirm that genes within this region contribute directly to the genetic susceptibility for AS.

Herpes simplex virus type 1 DNA persistence, progressive disease and transgenic immediate early gene promoter activity in chronic corneal infections in mice

We have used a mouse model system and the corneal route of inoculation to examine the issue of extra-neuronal persistence of herpes simplex virus type 1 (HSV-1). HSV-1 strain F DNA and inflammatory lesions were detected in corneal tissue of mice at 5, 11, 23, 37 and 60 days post-infection (p.i.) Viral DNA was localized by in situ PCR to epithelial cells and less frequently to cells in the stroma of the cornea. Viral proteins were not detected in the cornea and virus could not be isolated from tissue homogenates after 11 days p.i. even though histopathological lesions became progressively more severe at 37 and 60 days p.i. The DNA-containing cells were usually adjacent to the sites of inflammation or within these sites in the chronic stage (23, 37 and 60 days p.i.). In contrast to strain F, persistence of HSV-1 strain KOS DNA and inflammatory lesions were not detected after 11 days p.i.; this result suggests that the long-term persistence of HSV-1 DNA and the development of inflammatory lesions are virus strain-dependent. We tested for the possibility of transgenic HSV-1 immediate early gene (ICP4) promoter activity in chronically infected corneas of transgenic mice containing the ICP4 promoter fused to the bacterial beta-galactosidase coding sequence. Our results indicated that the chimeric transgene was expressed in the cornea at 5, 11, 23, 37 and 41 days p.i. Possible explanations for these results and mechanisms for the generation of the chronic inflammatory lesions are discussed. The properties of chronic HSV infections in the cornea may be similar to those which have been described for persistent or defective viral infections in other systems.

Brain 5-HT1C receptors and antidepressants

A variety of antidepressants of different chemical classes were tested for their in vivo and in vitro activity at 5-HT1C receptors in the brain. Conventional tricyclic antidepressants (imipramine, desipramine, maprotiline, clomipramine, trimipramine, amitriptyline, nortriptyline, doxepin, amoxapine, oxaprotiline) and two atypical antidepressants (mianserin and trazodone) were found to display affinity for 5-HT1C receptors in the nanomolar range. Antidepressants of other chemical classes and mechanisms of action (serotonin uptake inhibitors: fluoxetine, citalopram, sertraline, fluvoxamine; noradrenaline-dopamine uptake inhibitors: nomifensine, bupropion, amineptine; or monoamine oxidase inhibitors: moclobemide, iproniazid) had affinities in the micromolar range for 5-HT1C receptors, except fluoxetine. When tested in an in vivo functional model revealing agonistic or antagonistic properties at 5-HT1C receptors, all antidepressants displaying high affinity for this receptor type (except fluoxetine, clomipramine, trimipramine and oxaprotiline) were antagonists at 5-HT1C receptors. Antidepressants with lower 5-HT1C receptor affinity (except nomifensine) were inactive in this functional in vivo model. Antagonism at brain 5-HT1C receptors is a component of the antiserotonergic properties of a number of established antidepressants, especially of the tricyclic class.

HSV-2 DNA persistence in astrocytes of the trigeminal root entry zone: double labeling by in situ PCR and immunohistochemistry

A previous study using an in situ polymerase chain reaction (PCR) amplification method showed persistent herpes simplex virus type 2 (HSV-2) DNA sequences in brains of experimentally infected mice, particularly in cells of the pons near the trigeminal root entry zone. The present study was undertaken to identify the CNS cell type(s) that persistently harbor HSV DNA and to define the associated pathology. Tissue sections including the trigeminal root were immunoreacted to detect cellular antigens, then an HSV sequence was amplified in situ. During acute infection, the CNS portion of the trigeminal root was focally demyelinated and contained viral antigen and HSV DNA in glial cells. Following acute infection, no infectious virus of HSV antigen was detected. Demyelinated root lesions contained cells whose nuclei were similar in size to those of astrocytes and contained HSV-2 DNA by in situ PCR. With double labeling techniques, HSV DNA-containing nuclei were often associated with glial fibrillary acidic protein immunoreactivity, but not with that of neuron-specific enolase and only rarely with galactocerebroside or transferrin immunostaining. Thus, at least some of the cells containing persistent HSV DNA are astrocytes. Since HSV DNA is detected when no infectious virus can be isolated and no HSV antigen is found, we conclude that this astrocytic infection is non-productive. While in situ hybridization methods show HSV latency-associated transcript (LAT) RNA in neuronal nuclei during latent infections in trigeminal ganglia and, occasionally, in brain, we were unable to detect HSV-2 LAT RNA in astrocytes in these lesions, which suggests that persistent HSV infection of astrocytes may differ from neuronal latency.(ABSTRACT TRUNCATED AT 250 WORDS)

Terminal pattern elements in Drosophila embryo induced by the torso-like protein

The genes torso (tor) and torso-like (tsl) are two of the Drosophila maternal group genes implicated in a receptor tyrosine kinase signalling pathway that specifies terminal cell fate (reviewed in ref. 3). Loss-of-function mutations in these loci cause an identical phenotype in which pattern elements from the anterior (acron) and posterior (telson) ends have been deleted. We have cloned the tsl gene and demonstrate here that, in agreement with previous genetic data, it encodes a protein that is secreted and whose transcription is restricted to specialized categories of follicle cells localized at the poles of the egg chamber. At early blastoderm stage, tsl protein forms a symmetrical concentration gradient at the poles on the surface of the devitellinized embryo. Unrestricted expression of the tsl protein in tsl female mutants induces terminal pattern elements and suppresses the formation of abdomen in embryos. These results suggest that the tsl protein is the ligand that binds to the torso receptor.

Curative effects of the atypical antidepressant mianserin in the chronic mild stress-induced anhedonia model of depression

This study was designed to validate a novel animal model of depression by testing the curative effects of the atypical antidepressant mianserin. In this paradigm, the hedonic state of rats was assessed using an intracranial self-stimulation (ICSS) procedure. The ICSS threshold was determined before, during and after a 38-day period of exposure to a variety of intermittent, unpredictable, mild stressors. After 11 days of this regimen, the ICSS threshold was significantly higher in the stressed rats, suggesting a gradual decrease of sensitivity to reward. This "anhedonia" lasted throughout the stress regimen and progressively diminished over a 20-day period after stress was terminated. When stressed animals exhibiting anhedonia were treated with mianserin, the stress-induced increase in the ICSS threshold was gradually reversed over ten days of treatment. These results provide further support for the value of this anhedonia paradigm in modelling an important aspect of human depressive disorders.

Acute and chronic treatment with 5-HT reuptake inhibitors differentially modulate emotional responses in anxiety models in rodents

This study investigated behavioural effects of very potent 5-HT reuptake inhibitors after acute treatment (cianopramine and citalopram), as well as after chronic treatment (cianopramine), in two behavioural models of anxiety: 1) the light/dark choice procedure in mice and 2) the elevated plus-maze test in rats. In addition, the responses of mice to novelty in a free exploration paradigm were assessed after acute administration of both drugs. A single injection of cianopramine or citalopram increased neophobic reactions in the free exploration test. Furthermore, these drugs increased the avoidance reaction to a brightly illuminated chamber in the light/dark choice procedure as well as to open arms in the elevated plus-maze test. In contrast, after chronic treatment (10 mg/kg IP, once daily for 21 days) of cianopramine, anxiogenic-like effects were no longer produced in the light/dark choice paradigm whereas in the elevated plus-maze test, anxiolytic-like effects appeared. These results shed more light on the 5-HT hypothesis of anxiety, insofar as the increased availability of 5-HT resulting here from reuptake inhibition seems to initially result in an increased emotional reactivity which, however, subsequently disappears during chronic treatment.

In situ polymerase chain reaction: localization of HSV-2 DNA sequences in infections of the nervous system

To detect and localize a herpes simplex virus type 2 (HSV-2) thymidine kinase gene sequence in paraffin sections of brains and trigeminal ganglia of infected mice, an in situ polymerase chain reaction (ISPCR) protocol was developed. Using a single pair of primers, a 110 base pair DNA target sequence, and incorporation of a digoxigenin-labelled nucleotide during amplification, this procedure permitted rapid, specific, reproducible detection of infected cells. During acute brain infection, cells labelled by ISPCR were in the same infected foci that, in adjacent sections, contained viral antigen. This, together with controls, gave evidence of method specificity. In mice surviving acute infection, latently infected cells were labelled by ISPCR. In brains, focal areas contained labelled cell nuclei, and in trigeminal ganglia, neuronal nuclei were likewise labelled. Latent infection was confirmed by several methods, including identification of an HSV-specific sequence in DNA extracts of brains and ganglia, virus isolation from explanted ganglia, and HSV-2 latency-associated transcript (LAT) RNA localization in ganglionic neurons by in situ hybridization. Evidence in brains of ISPCR-labelled cells in regions where HSV-2 LAT-positive cells were not detected, and in ganglia of more ISPCR-labelled neurons than were LAT-positive, indicated that ISPCR is more sensitive in detecting latently infected cells than previous methods.

Acute and chronic administration of buspirone fails to yield anxiolytic-like effects in a mouse operant punishment paradigm

Drug-naive mice failed to exhibit antipunishment effects of ascending doses of buspirone (1-30 mg/kg, PO) in an operant punishment paradigm; however, these same mice subsequently exhibited increased punished responding after diazepam (10 mg/kg, PO). In a separate group of drug-naive mice, diazepam (1-30 mg/kg, PO)produced a robust antipunishment effect under identical experimental conditions, but crossover to buspirone (10 mg/kg, PO) failed to enhance punished responding. In a further experiment using this conflict model, two groups of benzodiazepine-experienced mice received daily oral administration of either vehicle or buspirone (5 mg/kg) for four weeks followed by a test with buspirone; neither group exhibited an antipunishment effect. Two other groups of benzodiazepine-experienced mice received either oral vehicle or diazepam (5 mg/kg) daily for four weeks followed by a test with diazepam; both groups exhibited a clear antipunishment effect. Finally, a group of benzodiazepine-experienced mice given vehicle daily for four weeks followed by a test with vehicle failed to exhibit an antipunishment effect. Thus, despite the attempt to optimize some important experimental conditions in this mouse conflict paradigm, buspirone still failed to produce an antipunishment effect. In contrast, diazepam consistently exhibited a robust anxiolytic-like effect under the same experimental conditions.

Environmental stimulation promotes changes in the distribution of phorbol ester receptors

The translocation of protein kinase C (PKC) from the cytosol to the membrane might be functionally involved in learning and memory. Using [3H]-phorbol 12,13-dibutyrate (3H-PDBu) binding three pools of binding sites could be distinguished in tissue preparations: Pool a comprised the soluble receptors which bound phorbol ester with low affinity in the absence of calcium. Pool b was composed of high-affinity phorbol ester binding sites identified in the soluble fraction upon addition of calcium. Pool c represented stably membrane-bound receptors binding phorbol ester independently of calcium. 3H-PDBu binding was then measured in the cortices and hippocampi of rats trained in an eight-arm radial maze. A progressive training-dependent increase of membrane-bound binding activity with a concomitant decrease in the soluble fraction was detected independent of learning the maze task. These results suggest that it is the experience of an enriched environment by the repeated behavioral stimulation in a maze rather than the acquisition of a memory task that leads to enhanced incorporation of phorbol ester receptors (PKC) into the cell membrane.

The multiplicity of actions of benzodiazepine receptor ligands

The benzodiazepine receptor is an allosteric modulatory site present on most, if not all, gamma-aminobutyric acid A (GABAA) receptor channels (GABAA-R). The benzodiazepine receptor recognizes a large spectrum of compounds from different chemical classes that are grouped together as benzodiazepine receptor ligands--of benzodiazepine and non benzodiazepine structure. The GABAA-R is thought to be a heteropentameric protein complex composed of at least three different classes of subunits, with each subunit comprised of up to six structural variants. Binding of GABA to the extracellular domain of the receptor causes a conformational change that opens the channel pore to anions. A classical benzodiazepine achieves a positive allosteric modulation of the GABA channel gating function by increasing the affinity of the receptor for GABA and, possibly, by facilitating the conformational transition from the closed to the open form (benzodiazepine receptor agonists). Inverse agonists of benzodiazepine receptors cause negative allosteric modulation (a decrease in the GABA activity). Benzodiazepine receptor antagonists bind to the benzodiazepine receptor with little effect on GABAA-R functioning. The intrinsic efficacy of benzodiazepine receptor ligands determines the direction and magnitude of allosteric modulation. Benzodiazepine receptor agonists affect neuronal activity in all major neuronal networks. The classical pharmacological profile of benzodiazepine receptor agonists consists of anxiolytic, anticonvulsant, sedative, and myorelaxant activities. Partial agonists of benzodiazepine receptors conserve anxiolytic and anticonvulsant activity, with greatly reduced sedation and muscle relaxation. They promise to present therapeutic advantages, in particular for long term use. In initial studies. they have produced fewer side-effects and showed reduced tolerance development and physical dependence liability.(ABSTRACT TRUNCATED AT 250 WORDS)

Neural antigen detection in mouse tissues is not impaired by decalcification

We examined whether EDTA decalcification decreases the sensitivity of antigen detection of formalin-fixed paraffin-embedded neural tissues. In undissected decalcified tissues, the immunoreactivities of select neural antigens were quantitatively compared with those in dissected sensory ganglia. Decalcification does not reduce either the numbers or staining intensities of antigen-positive neural cells. Tissues are well preserved and complex anatomical relationships are maintained.