Teflon coated stainless steel wire

Bipolar recording electrodes with tip length separation between 0.5 and 1.3 mm were constructed using Teflon-coated stainless steel wire (bare diameter, 125 μm; A-M Systems). Electrodes were implanted using predetermined coordinates from a stereotaxic atlas, using bregma as a landmark (Paxinos and Watson, 1998 ). Electrodes were cemented in place using dental acrylic and jeweller’s screws fastened into the skull.
For spatial profile field potential recordings in the HPC, we used a linear 16-contact (100 μm separation) microprobe arranged in a vertical linear array (U-probe, Plexon). The final depth of the probe was determined using the well established electrophysiological profile of theta field activity (Bland and Bland, 1986 (link); Buzsáki, 2002 (link)). The position of the multiprobe was histologically confirmed in every experiment by analyzing its track in relation to recorded field activity.

Electrodes were constructed from Teflon-coated, stainless steel wire, 178 µm in diameter (A-M Systems, Sequim, WA). Wire ends were stripped of Teflon and crimped to gold-plated male amphenol pins. The electrodes and oxygen-sensing probes were implanted 7 days before administration of the mTBIs, so electrographic and oxygenation data could be obtained immediately before and following injury induction. Rats were anesthetized with 5% isoflurane and then maintained with between 1% and 2% isoflurane for the remainder of the surgery. Lidocaine (2%) was administered subcutaneously at the incision site to alleviate suffering. Based on bregma, one bipolar electrode was chronically implanted under stereotaxic control in the ventral hippocampus (posterior 5.6 mm; right 5.2 mm; and 7 mm deep) with an oxygen-sensing optode (Oxford Optronix Ltd.) positioned in the dorsal hippocampus (posterior 3.5 mm; right 3.5 mm; 3.5 mm deep). As the impacts from the RmTBI were delivered to the left hemisphere, the optode and electrode were implanted into the right hemisphere, contralateral to the impact site, to reduce the risk of implant movement. The implants were adhered and anchored to the skull using dental cement and four stainless steel screws. One of the four screws served as a ground electrode.

Local-field potentials in response to auditory stimuli were recorded with a teflon-coated stainless steel wire (200 μm in diameter, A-M Systems, Chantilly, VA) positioned on the dura surface above the left auditory cortex. Continuous electrocorticogram was primarily amplified 10-fold, by using the AI 405 amplifier (Molecular Devices Corporation, Union City, CA, USA), high-pass filtered at 0.1 Hz, 200-fold amplified, and low-pass filtered at 400 Hz (CyberAmp 380, Molecular Devices Corporation), and finally sampled with 16-bit precision at 2 kHz (DigiData 1320A, Molecular Devices Corporation). The data were stored on a computer hard disk using Axoscope 9.0 data acquisition software (Molecular Devices Corporation) for later off-line analysis.