The evocation of rumination in sheep by the close-arterial injection of catecholamines, cholinergic drugs, autacoids and gastrointestinal hormones into the forestomach.

The effect of alpha-2 adrenoreceptor agonists, cholinergic drugs, autacoids and some gastrointestinal hormones upon the evocation of rumination in sheep when injected by close-arterial injection into the forestomach was examined. Apart from adrenaline, noradrenaline, dopamine and xylazine only one alpha-2 agonist (BHT933) evoked rumination effectively. Acetylcholine, neostigmine, the gastrointestinal hormones and the autacoids examined did not evoke rumination consistently. Tyramine did not usually evoke rumination and guanethidine injected before adrenaline did not prevent the latter from evoking rumination. The evocation of rumination by catecholamines does not appear to involve sympathetic, cholinergic or non-sympathetic non-cholinergic neurones in the enteric nervous system to activate the nervous sensory receptors involved in the reflex evocation of rumination.