ABSTRACT
A difference between stimulus-secretion coupling in epinephrine-containing cells and in norepinephrine-containing cells was discovered by Marley and Livett. This is important because it is well-known that different physiologic stimuli result in epinephrine and norepinephrine being secreted from the adrenal medulla in different ratios. The extent of pharmacologic and immunologic homology between the authentic nicotinic acetylcholine receptor from the periphery and a-bungarotoxin binding sites of PC12 cells and neuronal tissues were ascertained by Lukas. The phenomenon of desensitization of the nicotinic secretory response of adrenal chromaffin cells was reviewed by Marley. The secretion of catecholamines in response to nicotinic stimulation is known to diminish over time, and this generally has been attributed to loss of nicotinic receptor responsiveness. Desensitization of the receptor is accompanied by an increase in agonist affinity with no apparent change in antagonist affinity. The cardiac atria of mammals contain peptides, referred to as atrial natriuretic factors, that cause vasodilation and natriuresis.
