Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Boutons are specialised presynaptic compartments that lie along the axons of central neurons. Release of neurotransmitter from boutons is tightly regulated by the level of intracellular calcium [Ca2+]i. A rise in Ca2+ level may be generated in several ways; entry of extracellular Ca2+ via voltage gated calcium channels (VGCCs), entry via ligand-operated channels (LOCs) or the release of Ca2+ from intracellular Ca2+ stores. The role of Ca2+ stores in boutons remains poorly understood, despite recent work indicating that the release of Ca2+ from the endoplasmic reticulum (ER) may contribute to transmitter release. In this study we assess whether the lysosome or a closely related organelle functions as a Ca2+ store in the boutons of hippocampal pyramidal neurones. Lysosomes are small acidic organelles more commonly known for their role in degrading redundant cellular constituents. Using a fluorescent lysosomal marker, we show that lysosomes are located in the axons of hippocampal CA3 neurones. Selective pharmacological lysis of the lysosomes with glycyl-phenylalanine 2-naphthylamide (GPN) generates rapid, highly focal Ca2+ transients within the axon and increases the frequency of spontaneous miniature excitatory post-synaptic currents (mEPSCs), revealing that the organelle contains Ca2+ at a concentration sufficient to evoke transmitter release. Confocal laser scanning microscopy, combined with electrophysiology is used to monitor the action potential evoked increases in [Ca2+]i in boutons. We show that disruption of lysosomes compromises action potential evoked [Ca2+]i but this effect is occluded if the ER is discharged. Conversely, disruption of the lysosome does not appear to impact on the capacity of the ER to release Ca2+. These results suggest that the lysosome may serve as a Ca2+ store within hippocampal boutons, with a Ca2+ signalling role that is unique from that of the ER.

Original publication




Journal article



Publication Date





126 - 135


Amines, Animals, Animals, Newborn, Calcium, Dipeptides, Electric Stimulation, Enzyme Inhibitors, Excitatory Postsynaptic Potentials, Hippocampus, In Vitro Techniques, Lysosomes, Male, Microscopy, Confocal, Organelles, Presynaptic Terminals, Pyramidal Cells, Rats, Rats, Wistar, Thapsigargin, Time Factors