Fig. 2. Rapid formation of dendritic focal swelling in response to NMDA exposure. (A) Time-lapse confocal images of an apical dendrite of DiI-labeled CA1 pyramidal neuron following 10 minutes exposure to 30 µM NMDA. Numbers above the images indicate time (minutes) after NMDA treatment. NMDA induced a decrease in the number of spines and subsequently produced focal swelling along the dendrites. (B) Electron micrograph of varicosities in apical dendrites of DiI-labeled CA1 pyramidal neurons in untreated (a) and NMDA-treated (30 µM, 10 minutes) (b) slices. The varicosities, indicated by arrowheads, contained clear vacuoles (V) and many short fragments of degenerated microtubules.