Fig. 1.

Lcn-2 and behavioral stress exert a “push–pull” effect on dendritic spines in the hippocampus. (A) As described in PNAS (7), stress leads to an increase in both Lcn-2 and spine-density. However, Lcn-2 causes the opposite effect by decreasing spine numbers. (B) The same stress elicits an even greater increase in spine density in Lcn-2^−/− mice. (C) Hippocampal cells in unstressed, WT mice have a certain distribution of mature (mushroom-shaped) and immature (thin) spines adding up to control levels of spine density (gray horizontal line). Lcn-2 treatment lowers spine density and increases the relative proportion of thin spines (green downward arrow). In the absence of the brakes exerted by Lcn-2, stress creates a greater proportion of mushroom spines (Stressed Lcn-2^−/−) and further increases spine density (upward red arrow) relative to WT mice (upward black arrow).