NICOTINIC-EVOKED AND MUSCARINIC-EVOKED RELEASE OF CANINE ADRENAL CATECHOLAMINES AND PEPTIDES

The tissue content and overflow of norepinephrine (NE), epinephrine (Epi), dopamine (DA), Met-enkephalin (Met-Enk), and neuropeptide Y (NPY) from isolated, retrogradely perfused dog adrenal glands were studied. Under resting conditions, approximately 25% of the overflow of autocoids from the glands was Ca2+ dependent; the cholinergic antagonists hexamethonium and atropine had no effects on basal efflux. Stimulation with the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP; 3 or 50-mu-M) or with the muscarinic agonist pilocarpine (50-mu-M or 1 mM) evoked releases of autocoids. These releases were blocked or dramatically reduced by appropriate antagonists or by the removal of Ca2+ from the perfusate. Expressed as percentages of tissue stores, the rank order of overflow of autocoids was E approximately DA >> NE during resting conditions, DA >> E approximately NE during stimulation with 50-mu-M DMPP, and DA > Epi > NE during stimulation with 1 mM pilocarpine. These data are consistent with different mechanisms of release for the catecholamines, perhaps from different cell populations. The data support corelease of peptides and catecholamines, although clear pairing of autocoids could not be confirmed.