Selective Manipulation of Theta Oscillations in a Mouse Model

Abstract

Source: Bender, F. et al., Optogenetic Entrainment of Hippocampal Theta Oscillations in Behaving Mice. J. Vis. Exp (2018)

This video demonstrates a protocol to modulate theta oscillations in a genetically engineered mouse model with light-sensitive ion channels in its GABAergic medial septum neurons. By delivering light pulses to the hippocampus, the protocol aims to synchronize neuronal activity and generate theta oscillations, which are recorded as local field potentials.

Protocol

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.

PV-Cre knock-in male mice, 10-25 weeks old, were used. Mice were housed under standard conditions in the animal facility and kept on a 12-light/dark cycle.

1. Preparation of Tungsten Wire Arrays for LFP Recordings

1. Glue one optic fiber to the wire array so that the tip of the fiber is at the level of the shortest wire and the fiber tip is in close proximity, but not touching the tungsten wires. Keep the angle of the fiber as small as possible in order to prevent tissue damage during implantation.

2. Optogenetic Stimulation and Electrophysiological Data Acquisition

1. Check the light output from the patch cord. Estimate the light output from the fiber tip after connection depending on the transmission rate of the fiber implanted. Ensure that the light output from the fiber tip is between 5-15 mW to enable reliable entrainment.
2. Connect the headstage preamplifier to the chronically implanted connector. Connect the fiber optic patch cord to the chronically implanted hippocampal fiber for optogenetic stimulation experiments. In control light stimulation experiments, the optic fiber is connected to a dummy ferrule connected to the headset.
3. Place the mouse in the recording chamber.
4. Open the software to control the stimulus generator to generate the stimulation protocol.
5. Select the channel that controls the 473 nm DPSS laser.
6. Open the software of the recording system. Click on "ACQ" to acquire and "REC" to record. Wait before initiation of the light stimulation to record the baseline behavior (e.g., 2 min to retrieve baseline speed or 30 min to extract the baseline place fields).
7. Open the software to control the stimulus generator. Click "File > Open" and select the protocol file of choice. Click "Download and Start" to initiate the light stimulation.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
PV-Cre mice	The Jackson Laboratory	B6;129P2-Pvalbtm1(cre)Arbr/J
473 nm DPSS laser	Laserglow Technologies, Toronto, ON, Canada	R471005FX	LRS-0473 Series
593 nm DPSS laser	Laserglow Technologies	R591005FX	LRS-0594 Series
MC_Stimulus II	Multichannel Systems, Reutlingen, Germany	STG 4004
Tungsten wires	California Fine Wire Company, Grover Beach, CA, USA	CFW0010954	40 µm, 99.95%
Headstage	Neuralynx, Bozeman, Montana USA	HS-8	miniature headstage unity gain preamplifiers
LED	Neuralynx	HS-LED-Red-omni-10V
MATLAB	Mathworks, Natick, MA, USA
MC_Stimulus software	Multichannel, Systems
Multimode optic fiber	ThorLabs, Dachau, Germany	FG105LCA	0.22 NA, Low-OH, Ø105 µm Core, 400 - 2400 nm
Multimode fiber optic coupler	Thorlabs	FCMM50-50A-FC	1x2 MM Coupler, 50:50 Split Ratio, 50 µm GI Fibers, FC/PC