Fig. 1. Confocal images of leech Retzius neurons under isotonic and anisotonic conditions. Retzius neurons were loaded iontophoretically with the fluorescent dye Oregon Greens® 488 BAPTA-1. Under isotonic conditions (Control), the cell bodies of the neurons were ball shaped. Under hypertonic conditions (+85 mmol l^–1 NaCl, A), the neurons shrank and showed membrane invaginations. Under hypotonic conditions (–59 mmol l^–1 NaCl, B), the neurons swelled and showed evaginations (`blebs'). Images were taken after 5 min under anisotonic conditions.