{'fraction_non_alphanumeric': 0.04686584651435267, 'fraction_numerical': 0.03690685413005272, 'mean_word_length': 5.421052631578948, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A choline‐evoked [Ca2+]C signal causes catecholamine release and hyperpolarization of chromaffin cells

In bovine chromaffin cells fast‐superfused with Krebs‐HEPES solution containing 1–2 mM Ca2+, 5 s pulses of choline (1–10 mM), elicited catecholamine secretory responses that were only ~10% of those evoked by ACh (0.01–0.1 mM). However, in high‐Ca2+ solutions (10–20 mM) the size of the choline secretory responses approached those of ACh. The choline responses (10 mM choline in 20 mM Ca2+, 10Cho/20Ca2+) tended to decline upon repetitive pulsing, whereas those of ACh were well maintained. The confocal [Ca2+]c increases evoked by 10Cho/20Ca2+ were similar to those of ACh. Whereas 10Cho/20Ca2+ caused mostly hyperpolarization of chromaffin cells, 0.1ACh/20 Ca2+ caused first depolarization and then hyperpolarization; in regular solutions (2 mM Ca2+), the hyperpolarizing responses did not show up. In Xenopus oocytes injected with mRNA for bovine α7 nicotinic receptors (nAChRs), 10Cho/20 Ca2+ fully activated an inward current; in oocytes expressing α3β4, however, the inward current elicited by choline amounted to only 4% of the size of α7 current. Our results suggest that choline activates the entry of Ca2+ through α7 nAChRs; this leads to a cytosolic concentration of calcium ([Ca2+]c) rise that causes the activation of nearby Ca2+‐dependent K+ channels and the hyperpolarization of the chromaffin cell. This response, which could be unmasked provided that cells were stimulated with high‐Ca2+ solutions, may be the underlying mechanism through which choline exerts a modulatory effect on the electrical activity of the chromaffin cell and on neurotransmitter release at cholinergic synapses.