Exocytosis from large dense cored vesicles outside the active synaptic zones of terminals within the trigeminal subnucleus caudalis: a possible mechanism for neuropeptide release

[Cholinergic nerve endings: cellular function and molecular structure]

Progress made in the study of the cellular and molecular function of cholinergic nerve terminals suggests that the textbook schemes need to be extended. Vesicles contained in cholinergic nerve terminals not only store acetylcholine but also ATP and Ca2+ as well as peptides. These substances when co-released by exocytosis may modulate transmission both pre- and postsynaptically.

Adrenal enkephalin and catecholamine contents following subarachnoid hemorrhage in cats

A "closed space" subarachnoid hemorrhage (SAH) was produced experimentally in cats by rupture of the right middle cerebral artery to test the working hypothesis that a stressful event which provokes powerful sympathoadrenal discharge: causes a massive release of co-stored endogenous enkephalins together with catecholamines, induces an increased rate of opioid peptide precursor processing and/or synthesis, and eventually results in markedly elevated tissue levels of enkephalins relative to controls and to co-stored catecholamines. Adrenal medulla and other tissues were analyzed for met- and leu-enkephalins by RIAs and norepinephrine and epinephrine by HPLC-EC at 4 hrs, 3, 10, 16 and 30 days post-SAH. Catecholamines of adrenal medulla were already decreased at 4 hrs and by 3 days post-SAH depletion of epinephrine reached 86% and norepinephrine 53% compared to controls. Concurrently, at 4 hrs and 3 days post-SAH, the adrenal medulla was depleted 47% of met- and 53% of leu-enkephalins. By 10 days post-SAH, when catecholamines had regained control levels, met-enkephalin was elevated to 240% of control and 435% compared to the 3 day depletion; it remained elevated through 30 days post-SAH. In comparison, after 10 days reserpine treatment when catecholamines were markedly depleted, met-enkephalin rose to 970% and leu-enkephalin to 360% relative to controls, confirming recent reports in the literature. The data suggest that release of enkephalins originates primarily from epinephrine-type cells of the adrenal medulla in cat.