2 research outputs found
General Anesthetic Conditions Induce Network Synchrony and Disrupt Sensory Processing in the Cortex
General anesthetics are commonly used in animal models to study how sensory
signals are represented in the brain. Here, we used two-photon (2P) calcium
activity imaging with cellular resolution to investigate how neuronal activity
in layer 2/3 of the mouse barrel cortex is modified under the influence of
different concentrations of chemically distinct general anesthetics. Our
results show that a high isoflurane dose induces synchrony in local neuronal
networks and these cortical activity patterns closely resemble those observed
in EEG recordings under deep anesthesia. Moreover, ketamine and urethane also
induced similar activity patterns. While investigating the effects of deep
isoflurane anesthesia on whisker and auditory evoked responses in the barrel
cortex, we found that dedicated spatial regions for sensory signal processing
become disrupted. We propose that our isoflurane-2P imaging paradigm can serve
as an attractive model system to dissect cellular and molecular mechanisms
that induce the anesthetic state, and it might also provide important insight
into sleep-like brain states and consciousness
Quantitative Comparison of Genetically Encoded Ca2+ Indicators in Cortical Pyramidal Cells and Cerebellar Purkinje Cells
Genetically encoded Ca2+ indicators (GECIs) are promising tools for cell type-specific and chronic recording of neuronal activity. In the mammalian central nervous system, however, GECIs have been tested almost exclusively in cortical and hippocampal pyramidal cells, and the usefulness of recently developed GECIs has not been systematically examined in other cell types. Here we expressed the latest series of GECIs, yellow cameleon (YC) 2.60, YC3.60, YC-Nano15, and GCaMP3, in mouse cortical pyramidal cells as well as cerebellar Purkinje cells using in utero injection of recombinant adenoviral vectors. We characterized the performance of the GECIs by simultaneous two-photon imaging and whole-cell patch-clamp recording in acute brain slices at 33 ± 2°C. The fluorescent responses of GECIs to action potentials (APs) evoked by somatic current injection or to synaptic stimulation were examined using rapid dendritic imaging. In cortical pyramidal cells, YC2.60 showed the largest responses to single APs, but its decay kinetics were slower than YC3.60 and GCaMP3, while GCaMP3 showed the largest responses to 20 APs evoked at 20 Hz. In cerebellar Purkinje cells, only YC2.60 and YC-Nano15 could reliably report single complex spikes (CSs), and neither showed signal saturation over the entire stimulus range tested (1–10 CSs at 10 Hz). The expression and response of YC2.60 in Purkinje cells remained detectable and comparable for at least over 100 days. These results provide useful information for selecting an optimal GECI depending on the experimental requirements: in cortical pyramidal cells, YC2.60 is suitable for detecting sparse firing of APs, whereas GCaMP3 is suitable for detecting burst firing of APs; in cerebellar Purkinje cells, YC2.60 as well as YC-Nano15 is suitable for detecting CSs