Biomedical Engineering Reference
In-Depth Information
Anesthesia.
The rats were anesthetized by ketamine-hydrochloride (10 mg per 100 g
body weight, i.p., Ketanest S®, Pfizer, Karlsruhe, Germany) and xylazine (0,5 mg per
100 g body weight, i.p., Rompun
®
, Pfizer). Before surgery, the eyes of the rats were
medicated with Vidisic (Bausch and Lomb, Berlin Germany). After surgery, the
wound was sutured and the rats received 0.1 ml novaminsulfone (Ratiopharm, Ulm,
Germany) and 4 ml saline subcutaneously. Rats were exposed to red light (Petra, Bur-
gau, Germany) until normalization of vital functions.
6-Hydroxydopamine (6-OHDA) Lesioning.
The 6-OHDA
(
Sigma, Deisenhofen,
Germany) lesioning was performed by stereotactic surgery in adaption to Strauss et al.
[17]. The lesions of the right medial forebrain bundle of rats were induced by injec-
tion of 26 µg 6-OHDA in 4 µl saline with 1 g/l ascorbic acid delivered over 4 min via
a 5 µ l hamilton microsyringe (Postnova Analytics, Landsberg/Lech, Germany). The
coordinates relative to bregma were: anterior-posterior (AP) = -2.3 mm, medial-lateral
(ML) = 1.5 mm and dorsal-ventral (DV) = -8.5 mm [16].
Electrode Implantation.
Electrodes were implanted into the subthalamic nucleus
(STN), which is the most common target region for treatment of PD patients. The
surgical procedure was performed using a stereotactic frame (Stoelting, Wood Dale,
IL, USA) modified according to Harnack et al. [9]. To support the surgical procedure,
a cold light source (KL 1500 LCD, Schott, Mainz, Germany) was used in combina-
tion with a stereo-microscope (Leica, Wetzlar, Germany). The skull was opened by a
dental rose-head bur (Kaniedenta, Germany). The coordinates relative to bregma
were: anterior-posterior (AP) = -3.5 mm, medial-lateral (ML) = 2.4 mm and dorsal-
ventral (DV) = -7.6 mm [16]. A dental drill was used to bore an additional hole in the
skull for an anchor screw. The electrode was fixed to the skull by an adhesive-glue
bridge (Technovit 5071, Heraeus, Germany) to the anchor screw. After all, a subcuta-
neous wire was implanted. The suture exit hole was located in the middle of the back
of the rat.
The counter-electrodes (dental wires and suture clips in combination with the un-
ipolar electrodes) were implanted into the neck of the rats.
Chronical Instrumentation.
Commercial rat jackets (Lomir Biomedical, Quebec,
Canada) with a backpack were used to fix all electronic components of the miniatu-
rized custom-made stimulator system
(
Rückmann und Arndt, Berlin, Germany) to the
rat. The DBS stimulator and the battery were located in the backpack of the rat jacket.
The DBS electrode and the battery were connected to the DBS stimulator via plug
connectors (RS Components GmbH, Mörfelden-Walldorf, Germany). Both were sol-
dered with a lead-free solder tin (RS Components GmbH) and insulated with a bio-
compatible shrink tubing (RS Components GmbH).
Impedance Measurement.
Ten rats were used to measure the kinetics of the elec-
trode impedance alterations caused by the adventitia formation at the surface of un-
ipolar electrodes. During the measurement, the rats were anesthetized. The measuring
procedure was performed every day over a measuring period of 12 days (in experi-
ment 1) and over 22 days (in experiment 2). In the first experiment we used a dental
wire as counter-electrode and in the second step an array of suture clips (Allgaier
Instrumente GmbH, Frittlingen/Tuttlingen, Germany) to evaluate the influence of the
counter-electrode (shape and position) on the measurement results of the impedance.
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