Effects of aerosolized histamine and carbachol in the conscious horse.

Pulmonary function tests were performed in seven conscious, standing horses. Changes in pulmonary mechanics and ventilation volumes were measured after inhalation challenge with saline (baseline), histamine (1% w/v solution for 5 min) and carbachol (0.5% w/v solution for 3 min).

Preliminary pharmacological characterization of ovine mesenteric vasculature.

Spirally cut strips of ovine mesenteric vein and artery were studied in isolated organ baths. No qualitative differences were observed in the autonomic and autacoid reactivity of these blood vessels. Both arterial and venous preparations responded in a dose-related manner to 5HT greater than or equal to adrenaline greater than phenylephrine greater than histamine.

Characterization of H1- and H2-receptor function in pulmonary and systemic circulations of sheep.

We investigated the histamine H1- and H2-receptor function in the pulmonary and systemic circulations of sheep by in vivo and in vitro techniques. Combined H1 and H2 stimulation (by intravenous histamine) in vivo increased pulmonary vascular resistance (PVR) to 435% of base line and decreased systemic vascular resistance (SVR) to 49% of base line. Selective H2 stimulation (histamine after chlorpheniramine pretreatment) decreased PVR and SVR to 86 and 82% at base line, respectively, while selective H1 stimulation (histamine after metiamide pretreatment) increased PVR to 424% of base line and decreased SVR to 64% of base line.

Autacoid and autonomic reactivity of bovine and ovine bronchus: modifications by antigenic sensitization.

Spirally cut bronchial strips, prepared from three bovine (horse plasma-sensitized calves, control calves and adult cattle) and two ovine (horse plasma-sensitized and control sheep) animal groups were studied in isolated organ baths and their responses to standard autacoid and autonomic agents were compared. All bovine preparations contracted to carbachol greater than 5 HT greater than histamine and relaxed to isoproterenol greater than adrenaline greater than phenylephrine. Responses of ovine bronchus to the above agonists were similar to bovine except to histamine which caused relaxations.

Autonomic and autacoid activity in antigen-sensitized and control ovine pulmonary vein and artery.

Spirally cut strips of ovine pulmonary vein and artery were studied in isolated organ baths and their responses to selected autacoid and autonomic agents were compared. In addition blood vessels taken from horse plasma-sensitized sheep were compared with their respective controls. Pulmonary vein and artery exhibited qualitative and quantitative differences in their autacoid and autonomic reactivity.

Occurrence of inhibitory histamine H2-receptors in bovine pulmonary arteries.

The spirally cut strips of bovine pulmonary artery responded with contractions to 5HT greater than histamine and relaxed to isoproterenol, impromidine and greater than dimaprit. After complete H1-blockade with mepyramine, histamine caused weak relaxation of the tissues contracted with 5HT. Mepyramine competitively antagonized histamine-induced contractions while the relaxant responses of pulmonary arteries to impromidine and dimaprit were sensitive to cimetidine.

Autacoid and autonomic reactivity of sheep lung parenchymal strip and its modification by antigenic sensitization.

Lung parenchymal strips (LPS) of horse plasma-sensitized and control sheep were studied isometrically in isolated organ baths and their responses to autacoid and autonomic agents were compared. Control LPS responded with contractions to histamine greater than carbachol greater than 5HT and relaxed to isoproterenol greater than adrenaline greater than phenylephrine. In sensitized LPS, adrenaline and phenylephrine-induced relaxations were converted to contractions and a new order of potency and efficacy for spasmogens was observed i.

Bovine lung parenchyma strip has both airway and vascular characteristics. (Pharmacological comparisons with bronchus, pulmonary artery and vein).

Histamine and carbachol contracted the isolated lung parenchyma strip, bronchus, pulmonary artery and vein. Blood vessels and parenchyma strip responded with strong contractions to adrenaline and phenylephrine while bronchus was relaxed by these sympathomimetics. Isoprenaline relaxed all the partially contracted tissues.