Benech, Juan C

Brown, Euan R

Lima, Pedro A

Sotelo, José R

Synaptosomes from the optic lobes of squid (Loligo forbesi) were prepared by homogenization and allowed to settle onto glass coverslips. Synaptosomes were loaded with Ca2+ sensitive dyes (Fura-2 AM, Calcium Green-1 AM and Calcium Green-5N AM), visualized by light microscopy and Ca2+ sensitive fluorescence signals recorded and analyzed. With Fura-2, resting Ca2+ was found to be 80 nM (n = 10, SEM 5.7). Addition of K+ (30 mM), caffeine (3 mM) and thapsigargin (10 muM) evoked transient increases in cytoplasmic Ca2+. Addition of BAPTA-AM (20 muM) decreased intrasynaptosomal free Ca2+. Similar results were obtained with Calcium Green-1 AM but not with Calcium Green-5N AM. We conclude that synaptosomes from the squid optic lobe posses intact membranes and mechanisms to regulate intrasynaptosomal free [Ca2+], as well as caffeine sensitive Ca2+ stores. The results of this study are discussed with respect to the role of Ca2+ in presynaptic protein synthesis. (C) 2000 Wiley-Liss, Inc.</p

Ca2+ dynamics in synaptosomes isolated from the squid optic lobe

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