EEG, Evoked Potential, and Extracellular Single-Unit Recordings In Vivo - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 91

3. Procedures

EEG recording electrode . Epidural recording electrodes made from
# 0-80 × 1/8-inch stainless steel screws were placed at the following
stereotaxic coordinates (Paxinos and Watson, 1980): A-P +2.0 mm,
lateral ±3.0 mm and A-P −4.0 mm, lateral ±3.0 mm. Electrodes
were attached to a small plastic jack box, which is connected to the
EEG machine.
EP recording electrode . EP recording electrodes can be made from
either glass pipettes (containing 2 M NaCl ) or fi nal metal wire. In
our laboratory, we use a silver-ball recording electrode to measure
EP from the surface of the cerebellar cortex.
Single-unit recording electrode . Glass microelectrodes (5-10 M

3.1. Preparing
Electrodes

3.1.1. Recording
Electrodes

)
are fi lled with 2 M NaCl solution containing 2% pontamine sky
blue dye.

Ω

A bipolar tungsten stimulation electrode (World Precision
Instruments, Sarasota, FL) or a bipolar platinum wire (diameter
0.005

3.1.2. Stimulating
Electrodes

insulated by Tefl on, A-M System Inc.) stimulus electrode
(house made) is used in our laboratory for EP recordings.

″

Silver wire (0.025 , A-M System) coated with silver chloride is used

as reference electrode for EP and single-unit recordings. The refer-
ence electrode is wrapped with cotton soaked with 0.9% sodium
chloride and placed subcutaneously near the open skull. The reference
electrode is connected to the ground by taping it tightly onto the
ear bar of the stereotaxic frame.

″

3.1.3. Reference
Electrodes

We used the lithium/pilocarpine model in 10-week-old male
Sprague Dawley rats (approximately 160 g from Charles River
Laboratories) to induce SE following the procedure described by
Walton and Treiman ( 10 ). Rats were housed singly before surgery
with food and water available ad libitum with a 24-h diurnal light
cycle (lights on from 0700 to 1900 daily). At the time of electrode
placement, rats were anesthetized with 87 mg/kg ketamine
plus 13 mg/kg xylazine delivered by intraperitoneal injection
(IP). Epidural recording electrodes were placed at the following
stereotaxic coordinates ( 11 ): A-P +2.0 mm, lateral ±3.0 mm and
A-P −4.0 mm, lateral ±3.0 mm. The electrodes were attached to a
small plastic jack box, secured with dental acrylic, and the wound
was sutured. The animals were allowed to recover for at least 24 h
before further handling and given 1 week to recover from the
surgery before SE induction. Lithium chloride (3 mM/kg, i.p.)
was injected 12-24 h prior to the induction of SE. On the day of
the EEG recording, the rat was placed in the recording cage and
connected to a Grass-Telefactor EEG machine via a fl exible cable
suspended from the top of the cage, with an interposed commutator

3.2. Animal
Preparations

3.2.1. EEG Recordings
from a Status Epilepticus
Animal Model