Rapid odor perception in rat olfactory bulb by microelectrode array

Responses of 302 mitral/tufted (M/T) cells in the olfactory bulb were recorded from 42 anesthetized freely breathing rats using a 16-channel microwire electrode array.Saturated vapors of four pure chemicals,anisole,carvone,citral and isoamyl acetate were applied.After aligning spike trains to the initial phase of the inhalation after odor onset,the responses of M/T cells showed transient temporal features including excitatory and inhibitory patterns.Both odor-evoked patterns indicated that mammals recognize odors within a short respiration cycle after odor stimulus.Due to the small amount of information received from a single cell,we pooled results from all responsive M/T cells to study the ensemble activity.The firing rates of the cell ensembles were computed over 100 ms bins and population vectors were constructed.The high dimension vectors were condensed into three dimensions for visualization using principal component analysis.The trajectories of both excitatory and inhibitory cell ensembles displayed strong dynamics during odor stimulation.The distances among cluster centers were enlarged compared to those of the resting state.Thus,we presumed that pictures of odor information sent to higher brain regions were depicted and odor discrimination was completed within the first breathing cycle.

Accurate nanoelectrode recording of human pluripotent stem cell-derived cardiomyocytes for assaying drugs and modeling disease

The measurement of the electrophysiology of human pluripotent stem cell-derived cardiomyocytes is critical for their biomedical applications,from disease modeling to drug screening.Yet,a method that enables the high-throughput intracellular electrophysiology measurement of single cardiomyocytes in adherent culture is not available.To address this area,we have fabricated vertical nanopillar electrodes that can record intracellular action potentials from up to 60 single beating cardiomyocytes.Intracellular access is achieved by highly localized electroporation,which allows for low impedance electrical access to the intracellular voltage.Herein,we demonstrate that this method provides the accurate measurement of the shape and duration of intracellular action potentials,validated by patch clamp,and can facilitate cellular drug screening and disease modeling using human pluripotent stem cells.This study validates the use of nanopillar electrodes for myriad further applications of human pluripotent stem cell-derived cardiomyocytes such as cardiomyocyte maturation monitoring and electrophysiology-contractile force correlation.