Differential profile of Nix upregulation and translocation during hypoxia/ischaemia in vivo versus in vitro.

Nix, a hypoxia-sensitive member of the Bcl-2 family, is upregulated at the mRNA level during hypoxia through induction of a hypoxia-inducible factor-1 alpha (HIF-1 alpha) response element in its promoter sequence. However, the mechanism(s) regulating Nix protein activation remain unclear. The present studies examine Nix protein expression and subcellular distribution in response to hypoxic stimuli in vivo and in culture and to two disparate apoptotic stimuli in vitro.

Differential regulation of caspase-3 by pharmacological and developmental stimuli as demonstrated using humanised caspase-3 mice.

Caspase-3 is a potential therapeutic target for a number of degenerative diseases. However the development of specific caspase-3 inhibitors has been hampered by inter-species differences and the high degree of homology shared by different caspases. To circumvent these issues, we have produced and characterised a humanised caspase-3 mouse line (possessing one copy of the human gene with both copies of the murine gene disrupted) by crossing human caspase-3 transgenic mice with nullizygous caspase-3 knock-out mice.

Acquired QT interval prolongation and HERG: implications for drug discovery and development.

Putative interactions between the Human Ether-a-go-go Related Gene (HERG), QT interval prolongation and Torsades de Pointes (TdP) are now integral components of any discussion on drug safety. HERG encodes for the inwardly rectifying potassium channel (I(Kr)), which is essential to the maintenance of normal cardiac function. HERG channel mutations are responsible for one form of familial long QT syndrome, a potentially deadly inherited cardiac disorder associated with TdP.

Apoptosis is not an invariable component of in vitro models of cortical cerebral ischaemia.

Characterising the mechanisms of cell death following focal cerebral ischaemia has been hampered by a lack of an in vitro assay emulating both the apoptotic and necrotic features observed in vivo. The present study systematically characterised oxygen-glucose-deprivation (OGD) in primary rat cortical neurones to establish a reproducible model with components of both cell-death endpoints. OGD induced a time-dependent reduction in cell viability, with 80% cell death occurring 24 h after 3 h exposure to 0% O2 and 0.

Mice overexpressing human caspase 3 appear phenotypically normal but exhibit increased apoptosis and larger lesion volumes in response to transient focal cerebral ischaemia.

Caspase 3 activation has been implicated in cell death following a number of neurodegenerative insults. To determine whether caspase genes can affect the susceptibility of cells to neurodegeneration, a transgenic mouse line was created, expressing human caspase 3 under control of its own promoter. The human gene was regulated by the murine homeostatic machinery and human procaspase 3 was expressed in the same tissues as mouse caspase 3.

Nicotine improves sustained attention in mice: evidence for involvement of the alpha7 nicotinic acetylcholine receptor.

In humans, nicotine has been shown to improve attention in both normal and impaired individuals. Observations in rats reflect some, but not all aspects of the nicotine-induced improvements in humans. To date these findings have not been replicated in mice.

Comparison of effects of MgCl2 and Gpp(NH)p on antagonist and agonist radioligand binding to adenosine A1 receptors.

Aim: To investigate modulation of antagonist and agonist binding to adenosine A1 receptors by MgCl2 and 5 -guanylimidodiphosphate (Gpp(NH)p) using rat brain membranes and the A1 antagonist [3H]-8-cyclopentyl-1,3-dipropylxanthine ([3H]DPCPX) and the A1 agonist [3H]-2-chloro-N6-cyclopentyladenosine ([3H]CCPA).

Methods: Parallel saturation and inhibition studies were performed using well-characterised radioligand binding assays and a Brandel Cell Harvester.

Results: MgCl2 produced a concentration-dependent decrease (44%), whereas Gpp(NH)p increased [3H]DPCPX binding (19%).

[3H]dofetilide binding to HERG transfected membranes: a potential high throughput preclinical screen.

The pharmacological characteristics of [3H]dofetilide binding were examined in membranes prepared from human embryonic kidney (HEK293) cells stably expressing human ether-á-go-go related gene (HERG) K+ channels. The classIII antiarrhythmic compounds dofetilide, clofilium, 4'-[[1-[2-(6-methyl-2-pyridyl)ethyl]-4-piperidyl]carbonyl]methanesulfonanilide (E-4031), N-methyl-N-[2-[methyl-(1-methyl-1H-benzimidazol-2-yl)amino]ethyl]-4-[(methylsulfonyl)amino]benzene-sulfonamide (WAY-123,398) and d-sotalol all inhibited [3H]dofetilide binding. In addition, the structurally unrelated compounds pimozide, terfenadine and haloperidol, all of which prolong the QT interval in man, also inhibited binding.

Phenotyping complex behaviours: assessment of circadian control and 5-choice serial reaction learning in the mouse.

Currently, the behavioural phenotyping of mutant strains is restricted by the paucity of tests for the cognitive capabilities of mice. Most of the paradigms at present available such as the water maze or passive avoidance are dependent upon an aversive component for conditioning and as a consequence the data can often be confounded by the non-specific effects of stress. The development of mutant or transgenic mouse models of human diseases that effect cognitive function will require this confound to be overcome.

Characterisation of [(125)I]-apamin binding sites in rat brain membranes with HE293 cells transfected with SK channel subtypes.

The pharmacology of [(125)I]-apamin binding sites was examined in rat cortical and hippocampal tissue and compared with membranes prepared from human embryonic kidney (HEK293) cells transfected with SK channel subtypes hSK1, rSK2 and rSK3. The K(D) of [(125)I]-apamin in rat cortex and hippocampus was similar to the apamin-sensitive subtypes, rSK2 and rSK3 (K(D) (pM): 6.4, 7.

Effect of FK960, a putative cognitive enhancer, on synaptic transmission in CA1 neurons of rat hippocampus.

The action of FK960 [N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate], a novel cognitive enhancer, on excitatory synaptic transmission in the hippocampus was investigated. Excitatory postsynaptic potentials (EPSPs) and currents (EPSCs) were recorded intracellularly from CA1 neurons in rat hippocampus using the "blind patch" variant of whole-cell recording. FK960 (100 nM) significantly increased the amplitude of the EPSP, which was unchanged when changeover was made to control artificial cerebrospinal fluid (aCSF).

[3H]dofetilide binding in SHSY5Y and HEK293 cells expressing a HERG-like K+ channel?

The pharmacological characteristics of [3H]dofetilide binding in SHSY5Y, HEK293 and CHO-K1 cells were examined, and in parallel whole cell recordings used to characterise HERG-like K+ currents. Dofetilide affinity was similar in the human cell lines, SHSY5Y (Kd=99.6 nM) and HEK293 (Kd=102.

Overexpression of the human VPAC2 receptor in the suprachiasmatic nucleus alters the circadian phenotype of mice.

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) belong to a superfamily of structurally related peptide hormones that includes glucagon, glucagon-like peptides, secretin, and growth hormone-releasing hormone. Microinjection of VIP or PACAP into the rodent suprachiasmatic nucleus (SCN) phase shifts the circadian pacemaker and VIP antagonists, and antisense oligodeoxynucleotides have been shown to disrupt circadian function. VIP and PACAP have equal potency as agonists of the VPAC(2) receptor (VPAC(2)R), which is expressed abundantly in the SCN, in a circadian manner.

Behavioural analysis of the acute and chronic effects of MDMA treatment in the rat.

Rationale: A variety of animal models have shown MDMA (3,4-methylenedioxymethamphetamine) to be a selective 5-HT neurotoxin, though little is known of the long-term behavioural effects of the pathophysiology. The widespread recreational use of MDMA thus raises concerns over the long-term functional sequelae in humans.

Objective: This study was designed to explore both the acute- and post-treatment consequences of a 3-day neurotoxic exposure to MDMA in the rat, using a variety of behavioural paradigms.

Pyrazolopyridine derivatives act as competitive antagonists of brain adenosine A1 receptors: [35S]GTPgammaS binding studies.

The effects of adenosine receptor ligands and three novel pyrazolopyridine derivatives on guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding to rat cerebral cortical membranes were examined. [35S]GTPgammaS binding was stimulated in a concentration dependent manner by several adenosine receptor agonists. The adenosine A2a receptor selective agonist, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680), was ineffective confirming specificity for adenosine A1 receptor activation.

Pharmacological characterization of a simple behavioral response mediated selectively by central adenosine A1 receptors, using in vivo and in vitro techniques.

The behavioral profile of a range of adenosine receptor ligands was examined in rats using a locomotor activity model. Adenosine receptor agonists, including the selective A1 receptor agonist, N6-cyclopentyladenosine (CPA) and the A2A agonist, 2-[(2-aminoethylamino)carbonylethyl-phenylethylamino]- 5'-ethylcarboxa midoadenosine (APEC), reduced spontaneous motor activity in a dose-dependent manner. CPA-induced locomotor depression was attenuated by adenosine A1 receptor selective antagonists, such as 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), (R)-1-[(E)-3-(2-phenylpyrazolo[1, 5-a]pyridin-3-yl)-acryloyl]-2-piperidine ethanol (FK453), and (R)-1-[(E)-3-(2-phenylpyrazolo[1, 5-a]pyridin-3-yl)-acryloyl]-piperidin-2-yl acetic acid (FK352), but not by the A2A receptor antagonist, (E)-1,3-dipropyl-8-(3, 4-dimethoxystyryl)-7-methylxanthine (KF17837).

Species differences in brain adenosine A1 receptor pharmacology revealed by use of xanthine and pyrazolopyridine based antagonists.

1. The pharmacological profile of adenosine A1 receptors in human, guinea-pig, rat and mouse brain membranes was characterized in a radioligand binding assay by use of the receptor selective antagonist, [3H]-8-cyclopentyl-1,3-dipropylxanthine ([3H]-DPCPX). 2.

Neuroprotective actions of FK506 in experimental stroke: in vivo evidence against an antiexcitotoxic mechanism.

The cellular mechanisms underlying the neuroprotective action of the immunosuppressant FK506 in experimental stroke remain uncertain, although in vitro studies have implicated an antiexcitotoxic action involving nitric oxide and calcineurin. The present in vivo study demonstrates that intraperitoneal pretreatment with 1 and 10 mg/kg FK506, doses that reduced the volume of ischemic cortical damage by 56-58%, did not decrease excitotoxic damage induced by quinolinate, NMDA, and AMPA. Similarly, intravenous FK506 did not reduce the volume of striatal quinolinate lesions at a dose (1 mg/kg) that decreased ischemic cortical damage by 63%.

Tacrolimus (FK506) ameliorates skilled motor deficits produced by middle cerebral artery occlusion in rats.

Background And Purpose: Tacrolimus (FK506) is a potent immunosuppressant that is presently in clinical use for prevention of allograft rejection. Recently, animal studies reporting significant reductions in the volume of tissue damage associated with cardiac, hepatic, and cerebral ischemia suggest that tacrolimus may also be of use in the clinical management of stroke. In the present study, we examine whether the neuroprotective effects of tacrolimus, as assessed by histological outcome, are accompanied by an amelioration of the skilled motor deficits induced in the rat by middle cerebral artery occlusion (MCAO).

Comparison of the patterns of altered cerebral glucose utilisation produced by competitive and non-competitive NMDA receptor antagonists.

Recent studies indicate that competitive and non-competitive NMDA receptor antagonists can be readily distinguished by their effects on local cerebral glucose utilisation (1CGU). In the present study we compare the effects of the novel NMDA antagonist, (+)-1-methyl-1phenyl-1,2,3,4-tetrahydroisoquinoline (FR115427) on 1CGU, comparing its metabolic profile with that of the non-competitive NMDA receptor antagonist, dizocilpine (MK801) and of the competitive NMDA receptor antagonist CGS19755, using the 2-deoxyglucose metabolic mapping approach. Local cerebral glucose utilisation was measured in 80 anatomically discrete regions of the conscious rat brain using [14C]2-deoxyglucose quantitative autoradiography.