Fig. 1.

E2 rapidly and transiently enhances connectivity by increasing spine turnover. (A) EGFP-expressing cortical neurons (28 days in vitro) were treated with 10 nM E2 for 0, 5, 15, 30, and 60 min. Spine density increased transiently (blue line); average area decreased transiently (red line). (B) Time-lapse imaging of cortical neuron expressing EGFP. Cells were imaged for 60 min before treatment and then at 0, 5, 10, 15, 30, 45, and 60 min after treatment with E2. Red arrows indicate novel spines; red triangles represent persistent spines. (C) E2-treated cells were stained for bassoon. The total number of spines (black bar) and the number of spines colocalizing with bassoon (gray bar) were measured. (D) Schematic of brief, 5-min exposure of E2 experiment. Neurons were treated with E2 for 5 min (E2 pulse); cells were fixed at 0, 5, 15, 30, and 60 min from initial addition of E2. ***, P < 0.001. [Scale bars, 5 μm (A, C, and D); 1 μm (B).]