The emerging role of in vitro electrophysiological methods in CNS safety pharmacology

Abstract

Adverse CNS effects account for a sizeable proportion of all drug attrition cases. These adverse CNS effects are mediated predominately by off-target drug activity on neuronal ion-channels, receptors, transporters and enzymes - altering neuronal function and network communication. In response to these concerns, there is growing support within the pharmaceutical industry for the requirement to perform more comprehensive CNS safety testing prior to first-in-human trials. Accordingly, CNS safety pharmacology commonly integrates several in vitro assay methods for screening neuronal targets in order to properly assess therapeutic safety. One essential assay method is the in vitro electrophysiological technique - the 'gold standard' ion channel assay. The in vitro electrophysiological method is a useful technique, amenable to a variety of different tissues and cell configurations, capable of assessing minute changes in ion channel activity from the level of a single receptor to a complex neuronal network. Recent advances in automated technology have further expanded the usefulness of in vitro electrophysiological methods into the realm of high-throughput, addressing the bottleneck imposed by the manual conduct of the technique. However, despite a large range of applications, manual and automated in vitro electrophysiological techniques have had a slow penetrance into the field of safety pharmacology. Nevertheless, developments in throughput capabilities and in vivo applicability have led to a renewed interest in in vitro electrophysiological techniques that, when complimented by more traditional safety pharmacology methods, often increase the preclinical predictability of potential CNS liabilities.

Using Human Pluripotent Stem Cell-Derived Neural Cultures to Assess Safety of New Drugs and Chemicals

“…In spite of their importance, they have limited predictability, especially with drugs able to evoke a deleterious functional change but without noticeable biochemical or cellular changes. Electrophysiology techniques exploit ionic conductance of ion channels and transient modulation of the membrane potential of a neuron, being able to assess the functional status of the neural network in vitro [34]. There are many different techniques to record neuronal activity in vitro, with the most commonly used being the patch-clamp method.…”

“…There are many different techniques to record neuronal activity in vitro, with the most commonly used being the patch-clamp method. Although very sensitive, its low throughput and limitation of assessing only one or few neurons at a time precludes its use in investigating large neuronal circuitry dynamics [34]. Recently, new technologies of extracellular recordings have been developed.…”

“…Uniquely, MEA platforms consist of hundreds to thousands of electrodes integrated in a cell culture dish and enable recordings of neural activity by sensing extracellular field potentials [37]. This technology has been used to investigate the neural network dynamics of hESC-and hiPSC-derived neuronal cultures, organotypic slice cultures and acute brain slices [34]. By combining multiple arrays, the MEA technology allows to investigate several conditions at the time in a high-throughput fashion.…”

“…It needs to be noted though that the human brain contains hundreds of different types of neurons, each with unique properties and pharmacological signal transduction pathways which may not be fully recapitulated in vitro. When mimicking the human brain in vitro, it is imperative to select the most appropriate cellular model to ensure unequivocally adequate and highly reproducible predictability [34].…”

Is Consciousness Dissectible? Acute Slice Electrophysiology and a Bayesian Interpretation of Neural Correlates of Consciousness

“…At first glance, this question seems to be rather vague and based on too speculative premises in order to be answered directly, but it bears a degree of intuitive plausibility that renders it worth investigating. Hundreds of well-trained electrophysiologists use the acute slicing method to deepen our understanding of brain physiology on a daily basis [1][2][3][4][5] whilst the underlying basic question of what happens to an individuals' conscious states and contents is still unanswered. Recently, a method was capable to extend the lifespan of an acutely produced murine brain slice to more than 36 hours following preparation [3], which lends further relevance to the issue of whether any scientific statements can be made regarding the likelihood that some form of conscious experience might preserve on so produced brain slices.…”