Temperature- and concentration-dependence of kainate-induced γ oscillation in rat hippocampal slices under submerged condition

Abstract

Aim: Fast neuronal network oscillation at the γ frequency band (γ oscillation: 30-80 Hz) has been studied extensively in hippocampal slices under interface recording condition. The aim of this study is to establish a method for recording γ oscillation in submerged hippocampal slices that allows simultaneously monitoring γ oscillation and the oscillation-related intracellular events, such as intracellular Ca 2+ concentration or mitochondrial membrane potentials. Methods: Horizontal hippocampal slices (thickness: 300 μm) of adult rats were prepared and placed in a submerged or an interface chamber. Extracellular field recordings were made in the CA3c pyramidal layer of the slices. Kainate, an AMPA/kainate receptor agonist, was applied via perfusion. Data analysis was performed off-line. Results: Addition of kainate (25-1000 nmol/L) induced γ oscillation in both the submerged and interface slices. Kainate increased the γ power in a concentration-dependent manner, but the duration of steady state oscillation was reduced at higher concentrations of kainate. Long-lasting γ oscillation was maintained at the concentrations of 100-300 nmol/L. Under submerged condition, γ oscillation was temperature-dependent, with the maximum power achieved at 29 ºC. The induction of γ oscillation under submerged condition also required a fast rate of perfusion (5-7 mL/min) and showed a fast dynamic during development and after the washout. Conclusion: The kainite-induced γ oscillation recorded in submerged rat hippocampal slices is useful for studying the intracellular events related to neuronal network activities and may represent a model to reveal the mechanisms underlying the normal neuronal synchronizations and diseased conditions.

Subregional differences in the generation of fast network oscillations in the rat medial prefrontal cortex (mPFC) in vitro

“…) in vitro by bath application of a combination of 10 μ m Cb and 200 n m KA (Cb–KA) following which oscillations increased in magnitude over the first 2–3 h of recordings as reported in hippocampus (Lu et al . ; Pietersen et al . ).…”

“…In this study fast network oscillations were evoked in the mPFC (Fig. 1) in vitro by bath application of a combination of 10 μM Cb and 200 nM KA (Cb-KA) following which oscillations increased in magnitude over the first 2-3 h of recordings as reported in hippocampus (Lu et al 2012;Pietersen et al 2014). Recordings were initially made in three different areas of the PFC, the prelimbic (PrL), infralimbic (IL) and dorsopeduncular (DP) regions.…”

Dementia-related Bri2 BRICHOS is a versatile molecular chaperone that efficiently inhibits Aβ42 toxicity in Drosophila

“…Gamma oscillations were elicited by superfusing KA (100 nM) for at least 20 min to allow slices to stabilize; recordings were carried out in hippocampal area CA3 stratum pyramidale with ACSF-filled borosilicate glass microelectrodes pulled to a resistance of 3-5 . It should be noted that in vivo CA3 gamma oscillations have a peak frequency of ~30-40 Hz, however, in vitro, the peak frequency of gamma oscillations is usually somewhat lower owing to its dependence on the recording temperature (206). Electrophysiological recordings at room temperature for a long period of time cause early cell death, therefore the recording temperature is often kept around 34°C.…”

Local Optogenetic Induction of Fast (20–40 Hz) Pyramidal-Interneuron Network Oscillations in the In Vitro and In Vivo CA1 Hippocampus: Modulation by CRF and Enforcement of Perirhinal Theta Activity

“…All experiments were carried out at 25°C. In the submerged-type recording chamber, slices were continuously superfused with carbogenated physiological saline (5–6 ml/min flow rate according to Lu et al, 2012 ). Field potentials in the CA1 stratum pyramidale were recorded using glass microelectrodes (~1 MΩ open-tip resistance, filled with physiological saline) that were connected to an extracellular amplifier (EXT-01, npi electronic).…”