Midazolam

The drugs used in this study were administered intravenously via syringe or syringe pump. The base forms of alprazolam (Sigma-Aldrich, St. Louis, MO), midazolam and zolpidem (Tocris Bioscience, Bristol, UK) were dissolved in propylene glycol (50–80%), ethanol (5–10%), and sterile water. HZ-166 (8-ethynyl-6-(2’-pyridine)-4H-2,5,10b-triaza-benzo[e]azulene-3-carboxylic acid ethyl ester; Knutson et al., 2020 (link)) and βCCT (β-carboline-3-carboxylate-tert-butyl ester) were synthesized at the Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee and dissolved in 20% ethanol, 60% propylene glycol, and 20% sterile water. Dose selection is described in detail below in Results. All drug solutions were filter-sterilized prior to infusion (0.2 μm pore syringe filters).

Cocaine hydrochloride was provided by the National Institute on Drug
Abuse (Rockville, MD), midazolam (Hospira, Inc., 5 mg/mL) was purchased from the
pharmacy at the University of Mississippi Medical Center (Jackson, MS), and
zolpidem and L-838,417 were purchased from Tocris-Cookson (Ellisville, MO).
Cocaine and midazolam were prepared using 0.9% sterile saline, except during
some mixture conditions when cocaine was prepared using sterile saline mixed
with 20-80% propylene glycol to match the cocaine + test compound vehicle
delivered through the opposite lumen. Zolpidem and L-838,417 were dissolved in
propylene glycol and diluted in sterile saline to a final concentration of
20-80% propylene glycol (depending on drug concentration). Injections were
delivered over a 3-s infusion at a rate of 0.18 ml/s. All solutions were passed
through a 0.22 μm Millipore filter prior to administration.