Dexdomitor

Resting-state fMRI uses blood oxygenation level-dependent (BOLD) signal correlations as a measure of functional brain connectivity (Biswal et al., 1995 (link); Gorges et al., 2017 (link)). We used a T2-weighted magnetic resonance imaging sequence acquired with a 7 Tesla magnetic resonance scanner (Bruker BioSpin Pharmascan 70/16US). Subsequently, functional connectivity between a set of brain regions known to be related to cognitive functions (see below), such as cognitive flexibility and a high expression of NMDARs, was performed to characterize their age-related changes and the effects of D-serine on the aged rat brain.
The rats were food-deprived for a minimum of 12 h before starting the procedures. Anesthesia was induced with isoflurane (5%; Sofloran; PiSA) enriched with oxygen for 5 min. Once the animals were unresponsive, dexmedetomidine was administered (subcutaneous; Dexdomitor; Zoetis, 0.007 mg/kg) and the rats were placed in the scanner with the head fixed and maintained with isoflurane (0.25–0.50%) during the scanning session. Heart rate, breath rate, and spO2 were monitored continuously to assess the depth of anesthesia and general physiological condition of the animals. Body temperature was maintained by circulating warm water within the animal holder.

Kittens were anesthetized and gonadectomized after the baseline collections. All kittens were sedated with dexmedetomidine hydrochloride (Dexdomitor, Zoetis, Kirkland, QC, Canada) (10 ug/kg) and Buprenorphine (Zoetis, Kirkland, QC, Canada) (20 ug/kg) intramuscularly. After sedation, an IV catheter was placed in the cephalic vein for intravenous propofol (Fresenius Kabi Canada Ltd, Richmond Hill, ON, Canada) (1–4 mg/kg) induction. Once induced, cats were intubated and maintained on isoflurane and oxygen. The surgical procedure consisted of a vertical incision made through one side of the scrotum then the tunic to extrude the testicle. Attachment of the tunic was avulsed from the head of the epididymis and the pedicle was auto-ligated with a figure-eight knot. The testicle was then incised from the pedicle and was repeated on the contralateral side. Scrotal incisions were left to heal by secondary intention. Following surgical procedures, cats were given Robenicoxib (Zoetis, Kirkland, QC, Canada) (2 mg/kg) subcutaneously. For three days following gonadectomy cats were administered Robenicoxib (Zoetis, Kirkland, QC, Canada) (6 mg per cat) orally once per day to control post-operative pain. Daily care following gonadectomy procedures for all cats remained unchanged.

Animals were premedicated using intramuscular injections of ketamine (Ketasol^®, Richter Pharma, 50 mg/ml, 0.6 ml/kg bodyweight) and dexmedetomidine (Dexdomitor^®, Zoetis, 0.5 mg/ml, 0.2 ml/kg bodyweight). Maintenance of anesthesia was achieved using sevoflurane (Sevorane^®, AbbVie AG, Baar, Switzerland) dissolved in 4 l/min of 100% oxygen through an endotracheal tube (inner diameter 2.5 cm). Fentanyl (Fentanyl Hameln, 50 μg/ml, 0.2 ml/kg/h, Hameln pharmaceuticals GmbH, Hameln, Germany) was administered intravenously for analgesia. In addition, fluids and electrolytes were provided by crystalloid solution (Elo-Mel isoton, Fresenius Kabi, Graz, Austria) and lactate-buffered Ringer’s solution, respectively, to maintain physiological blood pH and electrolyte levels. Blood gas was regularly measured and kept within physiological ranges (pO₂: 95–100 mmHg, pCO₂: 35–45 mmHg, pH 7.35–7.45) by adjustment of the ventilation frequency (25-26/min) and of the tidal volume (10 ml/kg body weight).

The PD model was established using MPTP. For the mouse PD model, MPTP hydrochloride (25 mg/kg in saline, subcutaneous, Sigma–Aldrich, St. Louis, MO, USA) and probenecid (250 mg/kg in Tris-HCl buffer, Sigma–Aldrich) were administered over 4 weeks at 3.5-day intervals^{67 (link)}. The animals in the control group received a normal saline injection of the same dosage. The mice in PD+Rap and PD-DBS + 3BDO were injected with rapamycin (7.5 mg/kg/day, 7 days, Selleck Chemicals, Houston, TX, USA) and 3BDO (80 mg/kg/day, 7 days, Selleck Chemicals), respectively, four weeks after the first MPTP injection. For the monkey PD model, all animals were given general anesthesia with intramuscular injection of Zoletil (5 mg/kg, Virbac, Alpes-Maritimes, France) and Dexdomitor (20 μg/kg, Zoetis, NJ, USA), before being fixed on the bed of a digital subtraction angiography (DSA) in a supine position. The left femoral artery was punctured using the Seldinger method. The left internal carotid artery was catheterized, and 20 ml saline containing MPTP (0.4 mg/kg) was pumped (with a constant speed) over a 20 min period^{68 (link),69 (link)}. The monkeys in the control received a normal saline injection of the same dosage.

All rats were anesthetized with ketamine (75 mg/kg ip; Fort Dodge Laboratory) and Dexdomitor (0.5 mg/kg, ip Zoetis) to label carotid sinus nerve afferents as previously described (33 (link)). The anterograde fluorescent tracer DiA [4-Di-16-ASP (4-(4-(Dihexadecylamino) styryl)-N-Methylpyridinium Iodide; D3883, ThermoFisher, Waltham, MA] was applied unilaterally to the carotid body region and sealed in place with Kwik-Sil Silicone Adhesive (World Precision Instruments, Sarasota, FL). Atipamezole (Antisedan, 1 mg/kg ip; Pfizer Animal Health, New York, NY) was given to terminate anesthesia after surgery and the anti-inflammatory Rimadyl was administered after surgery. One week after the surgery, rats were exposed to either CIH or room air for 7 days.

Dogs were observed daily for general health using standard terms to record any abnormalities. Dog body temperatures were recorded for three weeks following the end of tick infestation (day 11 through day 32). Dogs were, in addition and specifically, observed daily for the presence or absence of lameness.
On days 48 and 49 (pre-treatment), blood samples were collected for the purpose of determining infection status of dogs using SNAP, Quant C6, and Lyme Multiplex assays. Additionally, two skin punch biopsies were collected from each dog in the dorsal cervical region, near the site where the ticks were released onto the animal. Biopsies were taken using a 4 mm punch biopsy under sedation using Dexdomitor® (dexmedetomidine hydrochloride; Zoetis) and Antisedan® (atipamezole hydrochloride; Zoetis) for reversal. The first punch biopsy was placed in Barbour-Stoenner-Kelly II (BSK II) medium for bacterial culture (data not shown) and the second was immediately frozen by placement on dry ice and stored at −20 °C until DNA isolation and PCR were performed as described [28 (link)].
Post-treatment blood samples for serum collection were obtained monthly (days 111, 145, 179, 221, 251, 281, 314) and post-treatment skin biopsies and PCR were performed on days 118, 146, 180 and at the end of the study on day 315.