Quintessential stereotaxic injector model 53311

All surgical procedures were performed as published in our prior work unless otherwise stated [29 (link),48 (link),49 (link)]. In order to prevent damage to noradrenergic neurons, each rat was pretreated with desipramine hydrochloride (12.5 mg/kg, prepared in 0.9% sterile saline with 10% dimethylsulfoxide (DMSO), i.p.; MilliporeSigma, St. Louis, MO, USA) 30 min prior to 6-OHDA exposure. Rats were then anesthetized with isoflurane (1.5–2.0%; VetOne, Boise, ID, USA) mixed in a vaporizer (JD Medical, Phoenix, AZ, USA) with 1.5 L of oxygen per min. 6-OHDA (5.0 µg/µL, prepared in 0.9% sterile saline with 0.02% ascorbic acid; MilliporeSigma, Burlington, MA, USA) was prepared fresh every 2 h. Using a microinjector (Stoelting Quintessential Stereotaxic Injector Model 53311, Stoelting Co., Wood Dale, IL, USA) connected to a syringe (10 µL; Hamilton Co., Reno, NV, USA) and needle (26 gauge; Hamilton Co.) two microliters (10 µg per coordinate) of 6-OHDA was administered (0.5 µL per min) unilaterally at two coordinates (in mm) within the medial forebrain bundle: AP-2.8, ML-1.8, DV-8.0 and AP-4.7, ML-1.5, DV-7.9, according to the Atlas of Paxinos and Watson, 2007 [56 ]. The syringe was left in place for 5 min post-injection to prevent the backflow of solution.

Rats were made hemi-parkinsonian through established protocols (Yue et al., 2014 (link)). Briefly, rats were anesthetized with isoflurane (1.5–2.0%; VetOne, Boise, ID) and fitted with a nose cone for continuous isoflurane administration. 6-OHDA was prepared in 0.9% sterile saline with 0.02% ascorbic acid; Millipore Sigma, Burlington, MA, United States) and was prepared fresh every 2 h. Using a microinjector (Stoelting Quintessential Stereotaxic Injector Model 53311, Stoelting Co., Wood Dale, IL, United States) connected to a syringe (10 μl; Hamilton Co., Reno, NV, United States) and needle (26 gauge; Hamilton Co.) 5 μg per coordinate of 6-OHDA was administered unilaterally at two coordinates (in mm) within the striatum: AP 1.6, ML 2.4, DV −4.0, and AP 0.2, ML 3.5, DV −6.4. Animals were given 12.5 mg/kg desipramine HCL in sterile 0.9% normal saline, with 10% dimethyl sulfoxide (DMSO; Sigma-Aldrich, St. Louis, MO) prior to delivery of 6-OHDA to prevent noradrenergic neuron damage.