Leann P. Quinn

The PPARγ agonist pioglitazone is effective in the MPTP mouse model of Parkinson's disease through inhibition of monoamine oxidase B

Background and purpose: The peroxisome proliferator‐activated receptor‐γ (PPARγ) agonist pioglitazone has previously been shown to attenuate dopaminergic cell loss in the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) mouse model of Parkinsons disease, an effect attributed to its anti‐inflammatory properties. In the present investigation, we provide evidence that pioglitazone is effective in the MPTP mouse model, not via an anti‐inflammatory action, but through inhibition of MAO‐B, the enzyme required to biotransform MPTP to its active neurotoxic metabolite 1‐methyl‐4‐phenylpyridinium (MPP+).

LABORAS™: Initial pharmacological validation of a system allowing continuous monitoring of laboratory rodent behaviour

A newly developed apparatus for automated behavioural analysis, Laboratory Animal Behaviour Observation, Registration and Analysis System (LABORAS), has been further validated with respect to the ability of the system to detect the pharmacodynamic effects of standard pharmacological tools. Data were obtained from rats administered with mCPP (reversal with SB242084), 8-OH-DPAT (reversal with WAY100635), amphetamine (reversal with haloperidol) and angiotensin, with the focus on locomotor activity, feeding and drinking behaviours. The data captured and analysed by LABORAS, suggests that the automated system is able to detect pharmacologically induced changes in behaviour, reliably and efficiently, with a significant reduction in the number of animals required, and reduced operator input.

Further validation of LABORAS™ using various dopaminergic manipulations in mice including MPTP-induced nigro-striatal degeneration

The automated behavioural apparatus, LABORAS (Laboratory Animal Behaviour Observation, Registration and Analysis System), has been further validated with respect to the ability of the system to detect behavioural impairments in mice, following various dopaminergic manipulations. Initially data were obtained from mice administered with amphetamine, haloperidol, SCH23390, apomorphine and L-DOPA, with the focus on locomotor and grooming activities. The data recorded by LABORAS on administration of these pharmacological tool compounds, is comparable with published findings using standard LMA systems and conventional observer methods. In addition the home cage behaviour of mice administered with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) using an acute dosing regimen was also investigated. In LABORAS, mice subjected to MPTP lesioning showed deficits in spontaneous motor activity at day 6-7 post-MPTP administration, over a 24 h test period, as compared to saline treated controls. The data captured and analysed using LABORAS, suggests that the automated system is able to detect both pharmacologically and lesion-induced changes in behaviour of mice, reliably and efficiently.

A beam-walking apparatus to assess behavioural impairments in MPTP-treated mice: Pharmacological validation with R-(−)-deprenyl

A beam-walking apparatus has been evaluated for its ability to detect motor impairments in mice acutely treated with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg, s.c., single or double administration). Mice subjected to MPTP lesioning showed deficits in motor performance on the beam-walking task, for up to 6 days post-MPTP administration, as compared to saline-treated controls. In addition, MPTP-treated mice were detected to have a marked depletion in striatal dopamine levels and a concomitant reduction in substantia nigra (SN) tyrosine hydroxylase (TH) immunoreactivity, at 7 days post-MPTP administration, indicative of dopaminergic neuronal loss. Pre-administration of the potent MAO-B inhibitor R-(-)-deprenyl at 3 or 10 mg/kg, 30 min, s.c, significantly inhibited the MPTP-induced reduction in SN TH-immunoreactivity, striatal dopamine depletions and impairments in mouse motor function. The data described in the present study provides further evidence that functional deficits following an acute MPTP dosing schedule in mice can be quantified and are related to nigro-striatal dopamine function.

Tricyclic azepine derivatives as selective brain penetrant 5-HT6 receptor antagonists

Starting from a benzazepine sulfonamide 5-HT(6) receptor antagonist lead with limited brain penetration, application of a strategy of conformational constraint and reduction of hydrogen bond donor count led to a novel series of tricyclic derivatives with high 5-HT(6) receptor affinity and excellent brain:blood ratios.

Postsynaptic 5-HT1B receptors modulate electroshock-induced generalised seizures in rats

1 Although an important regulatory role for serotonin (5‐HT) in seizure activation and propagation is well established, relatively little is known of the function of specific 5‐HT receptor subtypes on seizure modulation. 2 The aim of the present study was to investigate the role of 5‐HT1A, 1B and 1D receptors in modulating generalised seizures in the rat maximal electroshock seizure threshold (MEST) test. 3 The mixed 5‐HT receptor agonists SKF 99101 (5–20 mg kg−1 i.p.) and RU 24969 (1–5 mg kg−1 i.p.), 0.5 h pretest, both produced marked dose‐related increases in seizure threshold. These agents share high affinity for 5‐HT1A, 1B and 1D receptors. 4 Antiseizure effects induced by submaximal doses of these agonists were maintained following p‐chlorophenylalanine (150 mg kg−1 i.p. × 3 days)‐induced 5‐HT depletion. 5 The anticonvulsant action of both SKF 99101 (15 mg kg−1 i.p.) and RU 24969 (2.5 mg kg−1 i.p.) was dose‐dependently abolished by the selective 5‐HT1B receptor antagonist SB‐224289 (0.1–3 mg kg−1 p.o., 3 h pretest) but was unaffected by the selective 5‐HT1A receptor antagonist WAY 100635 (0.01–0.3 mg kg−1 s.c., 1 h pretest). This indicates that 5‐HT1B receptors are primarily involved in mediating the anticonvulsant properties of these agents. 6 In addition, the ability of the 5‐HT1B/1D receptor antagonist GR 127935 (0.3–3 mg kg−1 s.c., 60 min pretest) to dose‐dependently inhibit SKF 99101‐induced elevation of seizure threshold also suggests possible downstream involvement of 5‐HT1D receptors in the action of this agonist, although confirmation awaits the identification of a selective 5‐HT1D receptor antagonist. 7 Overall, these data demonstrate that stimulation of postsynaptic 5‐HT1B receptors inhibits electroshock‐induced seizure spread in rats.

A novel behavioural registration system LABORAS and the social interaction paradigm detect long-term functional deficits following middle cerebral artery occlusion in the rat.

Following stroke, patients suffer a wide range of disabilities including motor impairment, anxiety and depression. However, to date, characterisation of rodent stroke models has concentrated mainly on the investigation of motor deficits. The aim of the present studies was therefore to investigate home cage behaviour (as assessed by a recently developed automatic behavioural classification system, LABORAS) and social behaviour (as a measure of anxiety) in rats following transient middle cerebral artery occlusion (tMCAO). Rats subjected to tMCAO (90 min) showed deficits in general home cage behaviours including locomotion, rearing, grooming and drinking for up to 7 weeks post occlusion, as compared with sham operated controls. In addition, a significant decrease in the total duration of social interaction was also observed in occluded rats compared with shams. The data shows that in addition to motor deficits, animals display changes in home cage behaviour and decreased social behaviour which, in contrast to motor function, are prolonged over time. Transient MCAO in rats may therefore provide a pre-clinical model to investigate agents offering symptomatic relief for ischaemia-induced motor deficits and anxiety over time following injury.

Differential behavioral profiling of stimulant substances in the rat using the LABORAS™ system.

Preclinical testing requires rapid and reliable evaluation of the main in vivo effects of novel test substances usually in rodents. Nevertheless, the techniques primarily used up to now involve either automated measurement of motor activity or direct observation of behavioral effects by extensively trained investigators. The advantages of these approaches are respectively high-throughput and comprehensive behavioral assessment. Nevertheless, motor activity is only one aspect of animal behavior and it cannot predict the full neurobehavioral profile of a substance, whereas direct observation is time-consuming. There is thus a need for novel approaches that combine the advantages of both automatic detection and comprehensive behavioral analysis. In the present study, we used the LABORAS™ system to analyze motor and non-motor behavior in rats administered various stimulant substances with or without known psychotomimetic properties or abuse liability (amphetamine, cocaine dizocilpine (MK-801), ketamine, modafinil and nicotine). The data show that LABORAS™ clearly detects the stimulating effects on motor behaviors of amphetamine, cocaine, dizocilpine and ketamine in a dose- and time-dependent manner. Differential effects of these test substances on non-motor behaviors, such as grooming, eating and drinking could also be detected. Nicotine displayed only slight stimulating effects on locomotion, whereas modafinil was virtually without effect on the behaviors evaluated by the system. These data with different stimulant substances suggest that LABORAS™ presents an advantage over classical methods performing automated measurements restricted to locomotion. Furthermore, the procedure is considerably more rapid than behavioral observation procedures. Characterization of the behavioral profile of test substances using LABORAS™ should therefore accelerate preclinical studies. In addition, the multi-faceted parameters measured by LABORAS™ permit a more detailed comparison of the behavioral profiles of novel substances with standard reference substances, thereby providing important indicators for orienting further substance evaluation and supporting drug development.

P4-327: Effects of the novel 5-HT6 SB-742457 antagonist and the cholinesterase inhibitor donepezil in models of cognition

related to aging, Alzheimer’s disease (AD) and Schizophrenia. Thus serotonergic system became a potential target for the treatment of memory dysfunction. Methods: Our effective lead generation and optimization methods have resulted in a potent 5-HT6 receptor antagonist SUVN-502 with Ki of 1.71 nM. SUVN-502 exhibited antagonist like inhibition with EC50 of 0.103 M when tested for functional activity. SUVN-502 has more than 100 fold selectivity against the related GPCRs. The effective optimization of its critical physico-chemical properties has lead to oral bioavailability (31%) and brain penetration index (1.48). Results: SUVN-502 was effective in animal models of cognition. SUVN-502 reversed the age induced memory deficit in Morris water maze and novel object recognition task (NORT). SUVN-502 also reversed the spatial and working memory deficit induced by MK-801 and scopolamine in Morris water maze, NORT and radial arm maze task. The effective dose range of SUVN-502 in the above animal models was between 3 to 10 mg/kg. p.o. Brain microdialysis studies in rats with SUVN-502 showed significant increase in brain acetylcholine and glutamate levels correlating to the in vivo memory models. Conclusions: SUVN-502 has been identified as a candidate for clinical development for the symptomatic treatment of Alzheimer’s disease. SUVN-502 has completed all regulatory safety and toxicity studies to enter to human Phase-I clinical trials in 2008.