Associate Professor Worcester Polytechnic Institute, United States
Introduction:: Deep brain stimulation (DBS) has emerged as a promising therapeutic approach for a range of neurodegenerative and psychiatric disorders not limited to Parkinson’s disorder, obsessive-compulsive disorder, and epilepsy. However, as the human brain is an incredibly complex and dynamic organ, the mechanisms underlying therapeutic effects remain largely unknown. As studying the effects of stimulation on specific neural circuits requires implementing manipulation techniques unavailable to use in humans, we’ve developed a platform to explore how electrical stimulation alters neuronal excitability in C. elegans. In this work, we investigate how variations in system parameters including amplitude, frequency, and polarity impact responses in a rapid and repeatable manner. This platform allows for the investigation of the physiological consequences of devices and medications on the market, their concurrent effects, as well as optimization of their use.
Materials and Methods:: C. elegans nematodes in microfluidic devices containing two parallel trap arrays were exposed to either optogenetic, or both optogenetic and electrical stimulation. The optogenetic-only stimulation group was used as a control group. The strain used co-expresses a Chrimson channel rhodopsin excitable ion channel and GCaMP fluorescent calcium sensor in the AWA neuron. The emitted GCaMP signal observed at 617 nm is used to quantify changes in neural excitability and recorded via a widefield inverted fluorescent microscope. Each trial was 1 minute in duration and included a 10-second activation of the neuron via a red LED at 617 nm. Data collection was split into cycles comprised of 3 trials without electrical stimulation and three trials with constant electrical stimulation; the applied waveform had variable amplitude, a frequency of 20 Hz, and a 50% duty cycle. Individual neuron traces were extracted using the NeuroTracker ImageJ plug-in (Lagoy, 2013) and then imported to MATLAB for quantification of responses.
Results, Conclusions, and Discussions::
This platform provides a fully contained and automated method for studying electrical stimulation at the neuron level. The dynamic variation of stimulation parameters caused transient increases and decreases in neural excitability that was both rapid and repeatable. This platform may be used to study protein homologs to those affected within humans it becomes possible to identify non-invasive mechanisms for earlier diagnosis, minimize the effort required to find effective patient treatments, or understand how deep-brain stimulation may affect those with implants. Gaining a further understanding of neural modulation from an electro-physiological perspective also allows using a model system in which disease-related homologs can be used to decode clinically relevant behavioral biomarkers of neurodegenerative and neuropsychiatric diseases.
