Relative contribution of brain and peripheral connections to postnatal growth and cell accretion in the rat olfactory bulb.

Total weight and DNA (cell number) determination in whole olfactory bulbs (OB) revealed that unilateral transection of the olfactory peduncle in newborn rats causes 2 X more (40%) deficit in cell number in the operated OB than section of the olfactory nerve. The deficit due to combined operations ('isolation' of OB) were additive. Similar effects were observed on weight gain. It is inferred that both olfactory nerve and sources in the brain exert marked influences on postnatal cell accretion and growth in the OB and that the greater share of the brain is due to its direct contribution of new microneurons via the 'rostral migratory stream'.