Early postnatal development of the rat accessory olfactory bulb.

A volumetric study of the accessory olfactory bulb (AOB) in rats aged from birth (P0) to postnatal day 60 (P60) was conducted. AOB volume increased 600% from P0 to P18 and then declined, so that by P60, it was 66% of its maximum value. The growth of individual laminae paralleled overall AOB development, except for the internal plexiform layer, which continued to grow. The number of output neurons in the mitral cell layer declined after P18, while the total number of granule cells in the internal granular layer rose 300% from P0 to P18, but then did not change significantly through P60.