Comparative Analysis Of Basic Electrophysiological Characteristic Of Hippocampal CA1and CA3Neurons In Mice

ObjectiveThe basic electrophysiological properties of hippocampal CA1and CA3neurons arerecorded with patch clamp technique. The analytical and comparative results of basicelectrophysiological characteristics of hippocampal CA1and CA3neurons will providea theoretical foundation for memory and neurological disorders study.Methods1Preparation of mouse hippocampal slicesMice (20~40g and clean stage) about14days were anesthetized by1%sodiumpentobarbital with intraperitoneal injection (i.p). The head was quickly cut afteranedthetized, and the skull skin was scissored. Then the skull of the fixed brain was cutwith a pair of surgical scissors along the midline and both basal sides of the skull, at thesame time, the brain was perfused by a0C dissection solution (solution pre-filled withliquid95%O2+5%CO2gas mixture for30min). The olfactory bulb, and cerebellumof the brain were excised in a disk with0C dissection solution, and the twohemispheres skull were separated along the middle line with a scalpel and forceps inorder to remove the white and grey matters around the hippocampus. The brain blockafter trimmed was stood to the stage of brain slice machine by α-point blockcyanoacrylate glue. The groove containing brain block was quickly filled with a0Cdissection solution, which was continuously filled with a mixed gas. Brain slices of400m thick were cut along the sagittal direction. The slices were placed in a glass withartificial cerebrospinal fluid (ACSF), which was pre-filled with gas mixture for30min, incubated for1-2h at room temperature.2Fixing and perfuseing brain slicesA cover mesh fixation, namely U-shaped frame, which is made of U-shaped platinumgold pasted with rows of nylon cord. The U-shaped frame was gently put up on thebrain slices to prevent it moving. And the brain slices were soaked in2mm under ACSF,which was perfused by a peristaltic pump at a constant rate of1-2ml/min andsaturated with95%O2+5%CO2mixture.3Neuronal morphologyThe structural features of CA1and CA3neurons were observed with an infraredmicroscope (Japan) combining with a CCD camera system.4Electrophysiological recordingThe spontaneous excitatory postnaptic currents (sEPSCs) of CA1and CA3neuronswere recorded under the voltage clamp mode of holding potential at-60mV. Differention channel currents were induced and recorded by step pulse stimulation. The restingmembrane potential and action potential characteristics changes of hippocampalneurons were recorded under the current clamp mode. All cellular bioelectricity signalswere amplified by a patch clamp amplifier, and result figures were analyzed with IGORPro software.ResultsThe hippocampal tissue structure was observed clearly with healthy gloss and few deadneurons, and the hippocampal neurons were sealed easily with patch clamp technique.The spontaneous discharge current and action potential between CA1and CA3neuronsdid not show significant differences in amplitude (Amp), frequency (Fre), interspike-intervals (ISI) and resting membrane potentials (RP). The current densities ofsodium and potassium ions when injecting pulse stimulations and the action potentialnumbers when injecting step currents showed significant differences in CA1and CA3 neurons, the method of ChIP-Seq showed genes expression showed significantdifferences in CA1and CA3neurons (P <0.05).Conclusion1The Amp、Fre、RP and ISI of spontaneous discharge current and action potential ofCA1and CA3neurons of hippocampal slice showed no significant difference.2There was significant difference between depolarization pulse stimulation and sodiumand potassium ion channel current densities, as well as between step pulse current andAP numbers.3Some genes expression showed significant differences in CA1and CA3neurons.