Bestatin

Aripiprazole was injected subcutaneously into the plantar surface of the right hind paw (25 and 100 μg). The substance was provided by Bristol-Myers Squibb (Syracuse, NY, USA) and Otsuka Pharmaceuticals (Naruto, Tokushima, Japan). It was dissolved in physiological saline containing 5% tween 80; prostaglandin E₂ (PGE₂; hyperalgesic agent; Sigma®) was diluted in ethanol [14 (link)]. All other drugs used were diluted in saline, naloxone (nonselective antagonist at opioid receptors, Sigma), bestatin (an aminopeptidase-N inhibitor, Tocris®), clocinnamox (selective μ-opioid receptor antagonist, Sigma), nor-Binaltorphimine dihydrochloride (nor-BNI, selective κ-opioid receptor antagonist, Sigma), and naltrindole (selective δ-opioid receptor antagonist, Tocris).

The following drugs and chemicals were used: PnPP-19 (synthesized by China Peptides, China), the opioid receptor antagonist naloxone (Sigma, USA), the μ-opioid receptor antagonist clocinnamox (Tocris, USA), the δ-opioid receptor antagonist naltrindole (Tocris, USA), the κ-opioid receptor antagonist nor-binaltorphimine (Sigma, USA), the aminopeptidase inhibitor bestatin (Sigma, USA), AM251 [N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide; Tocris, USA], AM630 {6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl(4-ethoxyphenyl) methanone; Tocris, USA}, MAFP [(5Z,8Z,11Z,14Z)-5,8,11,14-eicosatetraenyl-methyl ester phosphonofluoridic acid, Tocris, USA] and VDM11 [(5Z,8Z,11Z,14Z)-N-(4-Hydroxy-2-methylphenyl)-5,8,11,14-eicosatetraenamide, Tocris, USA].
The drugs were dissolved as follows: PnPP-19 (saline), naloxone (saline), clocinnamox (saline), naltrindole (saline), nor-binaltorphimine (saline), bestatin (saline), AM251 and AM630 (12% DMSO in saline), MAFP (10% DMSO in saline), VDM11 (10% in saline) and injected at a volume of 2 μL into the lateral ventricle. The saline used for dilution of all drugs contained 0.5% Evans Blue.