Mk 801

All drug doses were calculated according to the active component of the salt. All drugs [morphine sulphate (3.75–120 mg kg⁻¹; Hameln Inc., Hameln, Germany), fentanyl citrate (0.2–4 mg kg⁻¹; Rotexmedica, Trittau, Germany), and naloxone hydrochloride (2 mg kg⁻¹; Ratiopharm, Ulm, Germany), used to precipitate withdrawal] were freshly prepared prior to use and were injected subcutaneously in lightly restrained, unanaesthetized mice at a volume of 10 μl g⁻¹ body weight. For chronic infusion with Alzet osmotic minipumps (1007D), fentanyl citrate salt (2 mg kg⁻¹ day⁻¹) and morphine sulphate salt pentahydrate (17 mg kg⁻¹ day⁻¹) were obtained from Sigma-Aldrich (St. Louis, MO). Drugs were diluted in phosphate-buffered saline for acute injections or dissolved in sterile water and then diluted in phosphate-buffered saline for osmotic pump delivery. For electrophysiology studies, MK-801 was obtained from HelloBio (Princeton, NJ). [Met⁵]enkephalin (ME), bestatin and thiorphan were from Sigma-Aldrich.

MK-801 (Hello Bio Inc., 304 Wall Street, Princeton, NJ 08540, USA) and scopolamine (Tocris Bioscience/Biotechne Corporation, Minneapolis, MN, USA) were dissolved in 0.9% saline. Spermine NONOate and DETA NONOate (Abcam, Cambridge, UK) were dissolved in 0.9% saline, and NPLA was dissolved in a small amount of DMSO and then adjusted to the proper volume with 0.9% saline. When the administration of experimental compounds was omitted (control, MK-801, or scopolamine group), the animals received appropriate vehicles. The doses used in behavioural experiments were based on our previous studies [8 (link)].

Naloxone and MK-801 were purchased from Hello Bio (Princeton, NJ). [Met⁵]enkephalin and CTAP were purchased from Sigma (St. Louis, MO). UK14304 tartrate and idazoxan were from Tocris (R and D system, Minneapolis, MN). Morphine alkaloid was obtained from National Institute on Drug Abuse, Neuroscience Center (Bethesda, MD) and was converted to HCl salt with 0.1 M HCl as a stock solution. All drugs were diluted to the tested concentrations in artificial cerebrospinal fluid (ACSF) and applied during superfusion. All salts used in electrophysiological experiments were purchased from Sigma.

MK-801 (Hello Bio, Bristol, UK), F15599 (NLX-101) (MedChemExpress) and VU0357017 hydrochloride (Biorbyt) were dissolved in 0.9% NaCl. VU0152100 (Biorbyt) and VU0238429 (Tocris) were dissolved in 10% Tween 80 in 0.9% NaCl. When the administration of the tested compounds was omitted (control and MK-801 groups), the animals received appropriate vehicles. The doses used in behavioral experiments were based on our previous studies [22 (link),23 (link)] and available data [25 (link),47 (link),48 (link)].

For all in vitro electrophysiology experiments, Pregnenolone sulphate (Sigma, UK) was prepared as 1 M stock using dimethyl sulfoxide (DMSO). A concentration of 100 µM was used for all electrophysiology experiments. MK-801 (Hello Bio, UK) was prepared with distilled water as 10 mM stock and used at 10 µM concentrations.