1. Pharmacological Provocation of Continuous Spike-wave Discharges (SWDs) in Genetically Prone WAG/Rij rat with i.p. injection of 2% Xylazine

This video demonstrates the acute effect of i.p. injection of 2% Xylazine in 16 months old female WAG/Rij rat. The rat was placed in a Plexiglas cage immediately after the i.p. injection of 2% Xylazine (Xyla, 20 mg/ml Xylazine hydrochloride, Interchemie Werken De Adelaar, the Netherlands) in dose of 2 mg/kg. Three-channels EEG signals were recorded using a multi-channel amplifier (PowerLab 4/35, ADInstruments), band-pass filtered between 0.5 and 200 Hz and digitized with 400 samples/second/per channel. The rat's behavior was recorded using a Genius eFace 1325R video camera.

Spike-wave discharges (SWDs) in the electroencephalograms are hallmark of absence epilepsy ^[1][2][3]. In rats with genetic predisposition to absence epilepsy, SWDs appeared spontaneously as a sequence of high voltage spikes and waves with a frequency of 8–10 Hz ^[4][5]. Figure 1 displays a three-channel electrocorticogram recording from a WAG/Rij rat. Epidural electrodes were implanted over the frontal cortex (symmetrically over the left and right sides) and over the right occipital cortex.

Figure 1. Spontaneous SWDs recorded in an 8-month-old female WAG/Rij rat and visualized in LabChart 8.0. Three-channel epidural EEG was recorded and abbreviated as FrL and FrR – frontal cortical left and right leads; OcR – occipital cortical lead. Time is given in mm:ss. The bottom graph shows an FFT power spectrum computed with 1024 size and 95,5 % window overlap. From ^[6] Supplementary under the terms of CC BY license 4.0.

Agonists of alpha2-adrenoreceptors (such as xylazine, clonidine, dexmedetomidine) are known to aggravate SWDs in genetically prone rats ^{[6][7][8][9][10][11][12][13]}. Xylazine is widely used in veterinary medicine as a sedative with analgesic and muscle relaxant properties ^[14][15]. In therapeutic doses, Xylazine induces continuous SWDs in genetically prone WAG/Rij rats, revealing its potential as a substance capable of pharmacologically provoking SWDs in rats.

2. ECoG examination in rats

Epidural electrodes were made of stainless-steel screws (screw: shaft length = 2.0 mm, head diameter = 2.0 mm, shaft diameter = 0.8 mm) providing recordings of electrical brain activity (EEG). The surgery was performed under isofluran anesthesia in a Kopf stereotaxic apparatus. Tree active epidural screw electrodes was implanted over the left/right frontal cortex (AP -/+2; L 2.5) and occipital cortex (AP −6; L 3); the fours reference screw electrode was placed over the right cerebellum. Coordinates are given in mm relative to the bregma. After the surgery, animals were housed individually under 12:12 h light:dark cycle (light on 8 a.m.) with free access to food and tap water. Recovery period lasted 10–14 days.