Adrenergic reactions of sheep rumen in vivo.

Pharmacodynamical analysis of alpha-adrenergic and beta-adrenergic reactions of sheep rumen was performed in vivo after administration of agonists and antagonists of alpha-adrenergic and beta-adrenergic receptors. It was found that phenylephrine, and in a lower degree propranolol, stimulated the motor activity of sheep rumen, while adrenaline, noradrenaline, isoprenaline, phenoxybenzamine and regitine depressed this activity. Propranolol abolished atonia produced by catecholamines in sheep rumen, and previous blockade of beta-adrenergic receptors with propranolol reversed the relaxing action of catecholamines on the muscular elements in the rumen. The experiments in vivo confirmed the adrenergic effects on the motor activity of the rumen of sheep obtained in earlier investigations on isolated muscles of the rumen. It is suggested that noradrenaline exerts an ambireceptro effect (similar to that of adrenaline) on the motor activity in sheep rumen.