In the present study, the hypoxaemic potential of four alpha 2 agonists possessing different selectivity for alpha 2 adrenoceptors and of a saline placebo was studied in five clinically healthy sheep using a randomized Latin square design and equipotent sedative doses. Baseline values for heart rate (HR), mean arterial pressure (MAP), arterial oxygen (PaO2)f and carbon dioxide (PaCO2) tensions, respiration rate and maximum change in pleural pressure (delta Ppl) were obtained, followed by the intravenous administration of either: xylazine (150 micrograms/kg); romifidine (50 micrograms/kg); detomidine (30 micrograms/kg); medetomidine (10 micrograms/kg) or placebo. Subsequent recordings were made up to 60 min after drug administration. No significant (P < or = 0.05) alterations in any variable occurred with placebo. All the alpha 2 agonists significantly (P < or = 0.05) decreased PaO2 levels without a significant (P < or = 0.05) change in PaCO2. The lowest PaO2 values were 29-42 mm Hg (3.9-5.5 kPa) with no significant difference between drugs. Respiratory rate and delta Ppl increased significantly within 2 min of drug administration; the duration of this effect varied with the alpha 2 agonist, lasting longest with romifidine. As compared to the saline treated group, a significant increase in MAP was observed up to 10 min after administration of romifidine and detomidine, however, a significant decrease was seen at 10 and 45 min after xylazine and medetomidine, respectively. The alpha 2 agonists studied induced a similar change in PaO2 at peak effect, despite their reported variable selectivity for alpha 2 vs. alpha 1 adrenoceptors.

Sch527123 [2-hydroxy-N,N-dimethyl-3-[[2-[[1(R)-(5-methyl-2-furanyl)propyl]amino]-3,4-dioxo-1-cyclobuten-1-yl]amino]benzamide] is a potent, selective antagonist of the human CXCR1 and CXCR2 receptors (Gonsiorek et al., 2007). Here we describe its pharmacologic properties at rodent CXCR2 and at the CXCR1 and CXCR2 receptors in the cynomolgus monkey, as well as its in vivo activity in models demonstrating prominent pulmonary neutrophilia, goblet cell hyperplasia, and mucus production. Sch527123 bound with high affinity to the CXCR2 receptors of mouse (K d ϭ 0.20 nM), rat (K d ϭ 0.20 nM), and cynomolgus monkey (K d ϭ 0.08 nM) and was a potent antagonist of CXCR2-mediated chemotaxis (IC 50 ϳ3-6 nM). In contrast, Sch527123 bound to cynomolgus CXCR1 with lesser affinity (K d ϭ 41 nM) and weakly inhibited cynomolgus CXCR1-mediated chemotaxis (IC 50 ϳ1000 nM). Oral treatment with Sch527123 blocked pulmonary neutrophilia (ED 50 ϭ 1.2 mg/kg) and goblet cell hyperplasia (32-38% inhibition at 1-3 mg/kg) in mice following the intranasal lipopolysaccharide (LPS) administration. In rats, Sch527123 suppressed the pulmonary neutrophilia (ED 50 ϭ 1.8 mg/kg) and increase in bronchoalveolar lavage (BAL) mucin content (ED 50 ϭ Ͻ0.1 mg/kg) induced by intratracheal (i.t.) LPS. Sch527123 also suppressed the pulmonary neutrophilia (ED 50 ϭ 1.3 mg/kg), goblet cell hyperplasia (ED 50 ϭ 0.7 mg/kg), and increase in BAL mucin content (ED 50 ϭ Ͻ1 mg/kg) in rats after i.t. administration of vanadium pentoxide. In cynomolgus monkeys, Sch527123 reduced the pulmonary neutrophilia induced by repeat bronchoscopy and lavage (ED 50 ϭ 0.3 mg/kg). Therefore, Sch527123 may offer benefit for the treatment of inflammatory lung disorders in which pulmonary neutrophilia and mucus hypersecretion are important components of the underlying disease pathology.Chronic obstructive pulmonary disease (COPD) is the fourth major cause of death in the United States and is characterized by irreversible airflow limitation due to chronic bronchitis or emphysema (Barnes and Stockley, 2005). The pathological hallmarks of COPD include peripheral airway inflammation dominated by neutrophils, the destruction of the lung parenchyma, submucosal gland hypertrophy, and goblet cell hyperplasia, as well as an increase in proinflammatory cytokines and chemokines (Barnes and Stockley, 2005). Current therapies for COPD are similar to those for asthma and include the use of ␤-adrenoceptor agonists, theophylline, muscarinic antagonists, and corticosteroids (Barnes and Stockley, 2005). However, these treatments do not prevent the progressive decline in lung function and demonstrate clinical activity in only a subpopulation of COPD patients. There is a strong correlation between disease Article, publication date, and citation information can be found at

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The cardiopulmonary effects of the intravenous administration of clonidine (15 micrograms/kg), ST-91 (30 micrograms/kg) and diazepam (0.4 mg/kg) were compared in five healthy sheep using a randomized cross-over design, to determine whether the hypoxaemic effects of alpha 2 adrenoceptor agonists are due to sedation, or to peripheral alpha 2 adrenoceptor stimulation. All three drugs significantly lowered arterial oxygen tension (PaO2) levels within 2 min of their administration; however, clonidine and ST-91 produced long lasting and severe hypoxaemia with mean PaO2 levels of approximately equal to 40 mm Hg and 50 mm Hg (5.3 kPa and 6.6 kPa), respectively. The fall in PaO2 was considerably less with diazepam (63 mm Hg or 8.4 kPa at 2 min) and by 15 min the values did not differ from placebo treated animals. None of the drugs increased arterial carbon dioxide tension (PaCO2) levels when compared to saline treatment and the acid base variables did not show any significant change. A significant increase was recorded in the packed cell volume of the ST-91 treated group throughout the study. Within 2 min of their administration, all drugs caused a significant increase in mean arterial pressure (MAP) as compared to the placebo treated group. The MAP remained significantly increased for 5 and 60 min after clonidine and ST-91 treatment, respectively. The study shows that ST-91 and clonidine produce a greater degree of hypoxaemia than occurs with diazepam sedation, and that the hypoxaemic effect of alpha 2 adrenoceptor agonists in sheep are mainly mediated by peripheral alpha 2 adrenoceptors.

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