An Optimized Methodology for the Neurobehavioural Assessment in Rodents

Introduction: The most widely used test to identify undesired effects of drugs on the central and the peripheral nervous system is the neurobehavioural observation battery adapted from that first described by Irwin in mice. As a neurobehavioural assessment is based on observations; thus, all factors involved need to be controlled and standardised to make the data collected objective, reproducible, reliable and predictive of safety liabilities. Methods: An observation battery comprising 58 signs with assigned full details of numerical scores was defined, and a standard design with associated recording, presenting and analysing data system was established. Validation studies were conducted with chlorpromazine, amphetamine, diazepam or clonidine given orally to rats or mice, in order to assess if this methodology could clearly differentiate the profile of effects produced by these compounds. The analysis of data from 80 control rats allowed for the assessment of the normal behaviour in order to characterise the inter-individual, daytime-related variability and the habituation of animals to the procedure. Results: The reference compounds induced their typical and expected transient effects on neurobehaviour, observed both in the home cage and open-arena, and on body temperature. In particular, amphetamine induced a stimulation of the nervous system activities and marked hyperthermia. Chlorpromazine, diazepam and clonidine induced depressive, anxiolytic or sedative effects associated with hypothermia. The analysis of data collected in control animals allowed for the identification of 6 signs which scored differently from the assigned normality at the first handling occasion due to the characteristic fear reactions to the unknown, and 9 signs at 8 h post-dose due to the animal's habituation to experimental conditions and handling. Discussion: The neurobehavioural changes expected by reference compounds administration were detected. These results confirm that by using this methodology the normal behaviour of the rat and the mouse, the daytime-related variability and the habituation of animals can be characterised, allowing a refined, reliable and reproducible neurobehavioural assessment of test substances in rodents

Cardioprotection by omega-3 fatty acids: Involvement of PKCs?

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G018 Evaluation of IKr blocking properties of different molecules with or without torsadogenic properties

Currently, industrials and regulatory authorities are worried by Torsades de Pointes (TdP), a type of ventricular tachycardia, which can lead to sudden death. The most recent guidelines from the International Committee of Harmonization, recommend to assess properly the risk of TdP, by different approaches, among others an in vitro method. This method consists on studying the blockade of a voltage-dependant potassium channel, called hERG. Indeed, hERG channel, responsible for the IKr current, seems to be blocked by the majority of the torsadogenic molecules and, is thus considered as an important marker of pro arrhythmic risk.CERB developed a bio-computerized database named TdPScreen® to predict the risk of TdP. Known molecules are classified according to their pro arrhythmic potential, from group A to C. The group A corresponds to drugs with numerous or several reports of TdP, the group B to compounds causing QT prolongation with TdP at very low frequency; and in group C to drugs with no report of TdP or QT prolongation. This database suggests that other factors than a single blockade of IKr could be involved in the genesis of druginduced TdP.We performed experiments in patch-clamp using HEK cells expressing stably the hERG channel. Different compounds from the different groups, above mentioned, were evaluated for their IKr blocking potency and compared to the TdPScreen® database.Results show some torsadogenic drugs might exhibit very low IKr blocking properties (e.g. D-sotalol), whereas other non-torsadogenic drugs are potent IKr inhibitors (e.g. verapamil, diltiazem…).These results, and others, indicate that drugs can block hERG current without any influence on TdP appearance.We conclude that assessing pro arrhythmic potential of compounds, only on the blocking effects of IKr, in vitro, can lead to the eviction of interesting molecules

The high frequency relationship: implications for torsadogenic hERG blockers

International audienceVentricular arrhythmias induced by human ether-a-go-go related gene (hERG; Kv 11.1 channel) blockers are a consequence of alterations in ventricular repolarisation in association with high-frequency (HF) oscillations, which act as a primary trigger; the autonomic nervous system plays a modulatory role. In the present study, we investigated the role of β1 -adrenoceptors in the HF relationship between magnitude of heart rate and QT interval changes within discrete 10 s intervals (sorted into 5 bpm heart rate increments) and its implications for torsadogenic hERG blockers