Muscarinic and nicotinic mechanisms in the responses of the adrenal medulla of the dog and cat to reflex stimuli and to cholinomimetic drugs.

In isolated perfused adrenal glands of the cat, muscarinic and nicotinic agonists selectively released adrenaline and noradrenaline respectively. In isolated perfused adrenal glands of the dog, the output of adrenaline and noradrenaline remained in a fixed ratio at rest and when stimulated by muscarinic or by nicotinic agonists. In the anaesthetized dog, a combination of muscarinic and nicotinic antagonists was needed to block reflex responses of the adrenal medulla. A nicotinic antagonist was more effective in blocking the baroreceptor reflex response than the chemoreceptor reflex response.