Journal: The European Journal of Neuroscience

Article Title: Maintaining network activity in submerged hippocampal slices: importance of oxygen supply

doi: 10.1111/j.1460-9568.2008.06577.x

Figure Lengend Snippet: Modified submerged slice chambers with single and dual superfusion. (A) Commercially available standard submerged slice chamber modified with an inert plastic insert to optimize the flow of artificial cerebrospinal fluid (ACSF) across the slice. (B) Scaled drawings of the top view and the cross-section of the chamber insert (in mm). (C) Low magnification of a submerged slice chamber with two fluid inlets and one outlet. (D) Schematic diagram of the flow in the dual superfusion chamber. (E) Picture taken at higher magnification of a chamber insert developed for dual superfusion. In this design, the slices were placed on a mesh glued between two plastic rings with a thickness of 2 mm. Two separate fluid inlets allowed ACSF to flow separately above and below the slice. (F) Scaled drawing (in mm) of the insert shown in E.

Article Snippet: The second modification allowed a double superfusion system to be used (Supertech Ltd, Pecs, Hungary; http://www.super-tech.eu ).

Techniques: Modification

Journal: The European Journal of Neuroscience

Article Title: Maintaining network activity in submerged hippocampal slices: importance of oxygen supply

doi: 10.1111/j.1460-9568.2008.06577.x

Figure Lengend Snippet: Generation and propagation of network events in submerged slice chambers. (A) Comparison of network activity recorded from hippocampal slices in an ‘Oslo’-style interface chamber and a modified submerged slice chamber with standard superfusion at low and high flow rates. (i) Spontaneous network activity recorded in an interface chamber (left), a submerged slice chamber at a low flow rate of 1.9 mL/min (middle), and a high flow rate of 5.2 mL/min (right). Note sharp wave – ripple activity in the interface chamber and only at a high flow rate in the submerged slice chamber. (ii) Cholinergically induced network activity in an interface chamber (left), and in a submerged slice chamber at a low flow rate (middle) and at a high flow rate (right). Note network oscillations in the interface chamber and only at a high flow rate in the submerged slice chamber. These recordings were made extracellularly in the pyramidal cell layer of CA3 of transverse hippocampal slices prepared from postnatal day 14–20 Wistar rats. Spontaneous sharp wave – ripple activity was recorded in slightly modified ACSF (see Materials and methods). After induction of fast network oscillations by bath application of 20 μ m carbachol in standard ACSF, recordings were taken after 15 min. Sharp wave – ripple events were digitally bandpass filtered between 0.1 and 500 Hz; fast network oscillations were low-pass filtered at 2 or 5 kHz. (B) Propagation of network events in a modified submerged slice chamber with dual superfusion. Sample traces of sharp wave – ripples (i) and cholinergically induced fast network oscillations (ii) recorded simultaneously in CA3 and CA1 of mouse hippocampal slices. These recordings were made in standard ACSF with a flow rate of 3–3.5 mL/min for each channel at 30–32 °C. The incidence and the peak amplitude of spontaneous sharp wave – ripples were comparable in both hippocampal regions (CA3, 1.3 ± 0.8 Hz and 418 ± 100 μV; CA1, 1.2 ± 0.9 Hz and 350 ± 118 μV; n =6; P >0.1, independent Student’s t -test). In the case of fast oscillations, the frequency of the network activity was not different (CA3, 30.4 ± 2.2 Hz; CA1, 30.8 ± 2.1 Hz; n =6; P >0.1, independent Student’s t -test), whereas the mean peak power was significantly smaller in CA1 than in CA3 (CA3, 275 ± 120 μV 2 /Hz; CA1, 41 ± 17 μV 2 /Hz; n =6; P <0.05, independent Student’s t -test).

Article Snippet: The second modification allowed a double superfusion system to be used (Supertech Ltd, Pecs, Hungary; http://www.super-tech.eu ).

Techniques: Comparison, Activity Assay, Modification

Journal: The European Journal of Neuroscience

Article Title: Maintaining network activity in submerged hippocampal slices: importance of oxygen supply

doi: 10.1111/j.1460-9568.2008.06577.x

Figure Lengend Snippet: Importance of oxygen levels for maintenance of spontaneous sharp wave – ripples. (A) Effect of flow rate on oxygen saturation and incidence of sharp wave – ripples recorded with a planar 8 × 8 microelectrode array. Black trace, oxygen saturation (%) during experiment; open circles, incidence of sharp wave – ripples (Hz); filled circles, amplitude of sharp wave – ripples (μV). Note the reduction of the incidence of sharp wave – ripples with lower oxygen saturation. The incidences were 1.1 ± 0.1 Hz, 1.3 ± 0.1 Hz and 0.4 ± 0.14 Hz (mean ± SEM) at flow rates of 6, 3 and 1.2 mL/min, respectively. The incidence at 1.2 mL/min was significantly lower than that at either 6 or 3 mL/min (both P <0.01, paired Student’s t -test, n =4 slices). The corresponding amplitudes were 28.0 ± 7.4 μV, 27.0 ± 8.2 μV and 23.3 ± 6.3 μV, respectively ( P >0.1, paired Student’s t -test, n =4 slices). (B) Plot of incidence of sharp wave – ripples against oxygen saturation modified by reduced flow rate ( n =4 slices; five or six data points per slice). Least-squares line fit superimposed. (C) Superfusion of the slice with artificial cerbrospinal fluid bubbled with 95% N 2 /5% CO 2 abolishes sharp wave – ripples. Black trace, oxygen saturation (%) during the experiment; open circles, incidence of sharp wave – ripples (Hz); filled circles, amplitude of sharp wave – ripples (μV). The incidences were 1.3 ± 0.1 and 0.3 ± 0.2 Hz (mean ± SEM; P <0.01, paired Student’s t -test, n =4 slices) with 95% O 2 /5% CO 2 and 95% N 2 /5% CO 2 , respectively. The corresponding amplitudes were 17.5 ± 3.1 μV and 16.3 ± 2.4 μV ( P >0.1, paired Student’s t -test, n =4 slices). (D) Plot of incidence of sharp wave – ripples against oxygen saturation modified by bubbling with 95% N 2 /5% CO 2 ( n =4 slices; five or six data points per slice). Tygon tubing with low permeability for O 2 was used in these experiments.

Article Snippet: The second modification allowed a double superfusion system to be used (Supertech Ltd, Pecs, Hungary; http://www.super-tech.eu ).

Techniques: Microelectrode Array, Modification, Permeability