E13+14 to E21
When consecutive daily injections are given to pregnant female rats on E13 and E14 (Figure 3), the intense labeling of the AOB output neurons stands out on E21. Over 60% of these neurons are generated on a single day—E13—and 8-9% are generated on E12, so over 90% are heavily labeled by the injections. (Bayer, 1983, Exp Brain Res 50:329-340). Most mitral cells in the MOB are labeled but only about 3-4% are generated on E12; 97% on or after E13; that is the reason for the intense label in nearly every mitral cell.
In all E21 specimens shown here, the olfactory recess of the lateral ventricle has an area where the ventricular lining is ruptured, and cells ooze out into the lumen. This is seen in EVERY SPECIMEN on or after E19 and some E18 specimens that are more advanced. We have no idea of the significance of this phenomenon, but its consistent appearance indicates that this is not a processing artifact.