Ca(2+) dynamics in synaptosomes isolated from the squid optic lobe.

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Synaptosomes are crucial for understanding neurotransmission.
• Calcium ions (Ca2+) play a vital role in synaptic function and presynaptic processes.
• Investigating calcium regulation in invertebrate models offers insights into conserved mechanisms.

Purpose of the Study:

• To characterize the calcium dynamics within isolated squid optic lobe synaptosomes.
• To assess the integrity of synaptosomal membranes and their calcium regulatory mechanisms.
• To explore the presence of caffeine-sensitive intracellular calcium stores.

Main Methods:

• Preparation of synaptosomes from squid (Loligo forbesi) optic lobes.
• Loading synaptosomes with Ca2+-sensitive fluorescent dyes (Fura-2 AM, Calcium Green-1 AM, Calcium Green-5N AM).
• Microscopic visualization and quantification of Ca2+-sensitive fluorescence signals.

Main Results:

• Resting intracellular Ca2+ concentration was determined to be 80 nM using Fura-2.
• Stimulation with K+, caffeine, and thapsigargin induced transient increases in cytoplasmic Ca2+.
• BAPTA-AM treatment reduced intrasynaptosomal free Ca2+, confirming membrane integrity and calcium buffering.
• Calcium Green-1 AM yielded similar results, while Calcium Green-5N AM did not.

Conclusions:

• Squid optic lobe synaptosomes possess intact membranes and functional mechanisms for regulating intracellular Ca2+.
• Evidence suggests the presence of caffeine-sensitive intracellular Ca2+ stores within these synaptosomes.
• The study provides a foundation for further research into the role of Ca2+ in presynaptic protein synthesis.