Accepted

S-nitrosothiols exert multiple effects on neural processes in the central and peripheral nervous system. This study shows that intravenous infusion of S-nitroso-L-cysteine (SNO-L-CYS, 1 μmol/kg/min) in anesthetized male Sprague Dawley rats elicits (a) sustained increases in minute ventilation, via increases in frequency of breathing and tidal volume, (b) a decrease in Alveolar-arterial (A-a) gradient, thus improving alveolar gas-exchange, (c) concomitant changes in arterial blood-gas chemistry, such as an increase in pO and a decrease in pCO, (d) a decrease in mean arterial blood pressure (MAP), and (e) an increase in tail-flick (TF) latency (antinociception). Infusion of S-nitroso-D-cysteine (SNO-D-CYS, 1 μmol/kg/min, IV), did not elicit similar responses, except for a sustained decrease in MAP equivalent to that elicited by SNO-L-CYS. A bolus injection of morphine (2 mg/kg, IV) in rats receiving an infusion of vehicle elicited (a) sustained decreases in frequency of breathing tidal volume, and therefore minute ventilation, (b) a sustained decrease in MAP, (c) sustained decreases in pH, pO and maximal sO with sustained increases in pCO and A-a gradient, and (d) a sustained increase in TF latency. In rats receiving SNO-L-CYS infusion, morphine elicited markedly smaller changes in minute ventilation, arterial blood gas chemistry, A-a gradient and MAP. In contrast, the antinociceptive effects of morphine were enhanced in rats receiving the infusion of SNO-L-CYS. The morphine-induced responses in rats receiving SNO-D-CYS infusion were similar to vehicle-infused rats. These data are the first to demonstrate that infusion of an S-nitrosothiol, such as SNO-L-CYS, can stereoselectively ameliorate the adverse effects of morphine on breathing and alveolar gas exchange while promoting antinociception.

Drugs targeting mu opioid receptors are the mainstay of clinical practice for treating moderate-to-severe pain. While they can offer excellent analgesia, their use can be limited by adverse effects, including constipation, respiratory depression, tolerance, and abuse liability. Multifunctional ligands acting at mu opioid and nociceptin/orphanin FQ peptide receptors might provide antinociception with substantially improved adverse-effect profiles. This study explored one of these ligands, OREX-1038 (BU10038), in several assays in rodents and nonhuman primates. Binding and functional studies confirmed OREX-1038 to be a low-efficacy agonist at mu opioid and nociceptin/orphanin FQ peptide receptors and an antagonist at delta and kappa opioid receptors with selectivity for opioid receptors over other proteins. OREX-1038 had long-acting antinociceptive effects in postsurgical and complete Freund's adjuvant (CFA)-induced thermal hyperalgesia assays in rats and a warm water tail-withdrawal assay in monkeys. OREX-1038 was active for at least 24 h in each antinociception assay, and its effects in monkeys did not diminish over 22 days of daily administration. This activity was coupled with limited effects on physiological signs (arterial pressure, heart rate, and body temperature) and no evidence of withdrawal after administration of naltrexone or discontinuation of treatment in monkeys receiving OREX-1038 daily. Over a range of doses, OREX-1038 was only transiently self-administered, which diminished rapidly to nonsignificant levels; overall, both OREX-1038 and buprenorphine maintained less responding than remifentanil. These results support the concept of dual mu and nociceptin/orphanin FQ peptide receptor partial agonists having improved pharmacological profiles compared with opioids currently used to treat pain.

Sickle cell disease (SCD) is one of the most common inherited diseases worldwide. It is associated with lifelong morbidity and a reduced life expectancy. Hydroxyurea (hydroxycarbamide), an oral chemotherapeutic drug, ameliorates some of the clinical problems of SCD, in particular that of pain, by raising foetal haemoglobin (HbF). This is an update of a previously published Cochrane Review.