Activation of a single spine recruits a lysosome to the base of the spine. (A) Experimental timeline of two-photon imaging and MNI-glutamate uncaging in hippocampal organotypic cultures. Individual spines on secondary dendrites of CA1 pyramidal neurons were visualized with a laser tuned to 900 nm. A 720-nm laser was used to stimulate individual spines, using 0.5-ms pulses at 1 Hz for 1 min. Stimulation was done with MNI-glutamate (2.5 mM MNI-glutamate) or without (“mock uncaging”) as a control in ACSF containing 0 mM Mg²⁺. Arrows signal the time points at which the representative images from B and C were taken. (B and C) Representative images of a secondary dendrite in a CA1 pyramidal neuron in a rat organotypic hippocampal slice. Time points are 5 and 2 min before uncaging and 2 min and 5 min after uncaging. (D) Mean dwell time for a lysosome at the base of a spine in either control or MNI-glutamate conditions. *, P ≤ 0.05, Mann–Whitney U test. Data represent mean ± SEM. (E) Cumulative probability distribution for each condition with and without (mock uncaging) MNI-glutamate. n = 12 for control, 10 for uncaging. P ≤ 0.01, Kolmogorov–Smirnov test. Experimenter was blinded to condition upon analysis.