Yohimbine hcl

Fentanyl HCl was acquired from the National Institute on Drug Abuse (NIDA Drug Supply Program, Rockville, MD) and dissolved in 0.9% bacteriostatic saline to make the doses used for self-administration (2.5 μg/kg per 0.1 ml infusion volume) or fentanyl-induced reinstatement (15 or 30 μg/kg delivered via subcutaneous [s.c.] injection). The α2 adrenergic antagonist yohimbine HCl (Sigma-Aldrich, St. Louis, MO) was dissolved in sterile water to prepare the two yohimbine-induced reinstatement doses (1 or 2 mg/kg delivered via intraperitoneal [i.p.] injection). yohimbine solutions were mixed the day prior to reinstatement and stored at 4°C under aluminum foil until needed. All doses were based on salt weight.

[2-[4-[(2-Chloro-4,4-difluorospiro[5H-thieno[2,3-c]pyran-7,4′-piperidine]-1′-yl)methyl]-3-methylpyrazol-1-yl]-3-pyridyl]methanol (LY2940094; (Toledo et al., 2014 (link))) was synthesized at Lilly Research Laboratories (Madrid, Spain). Naltrexone HCl and yohimbine HCl were purchased from Sigma-Aldrich (St. Louis, MO and Milan, Italy, respectively). 95% Ethanol was diluted to 15% (v/v) in tap water for experiments in P rats and 10% (v/v) in distilled water for experiments in msP rats. LY2940094 was dissolved in 20% Captisol in 25 mM phosphate buffer (pH 3, adjusted for L-tartaric acid salt weight), and administered orally in a volume of 2–3 ml/kg. Yohimbine and naltrexone were dissolved in distilled water and injected IP and PO, respectively (1 ml/kg). Solutions were prepared fresh daily.