Long-lasting increase of cholinergic enzyme activities in diagonal band and olfactory bulb after postnatal intrabulbar injection of NGF in rat

The effect of a single dose of 1 ng nerve growth factor (NGF) injected into the right side of the olfactory bulb (OB) of postnatal 5-day-old rats on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in the horizontal limb of the diagonal band of Broca (HDB) and in the OB was analysed. Animals were sacrificed at day 40 following treatment. As compared to the control sham-operated rats, NGF treatment increased ChAT and AChE activities in the ipsilateral HDB by 37% and 24%, respectively. Total enzyme activities in the treated OB significantly increased, ChAT by 52% and AChE by 30%, however specific activities expressed per g proteins were not changed. The wet weight and protein content of NGF-treated OB were insignificantly increased. Our findings indicating a long-lasting trophic effect of exogeuously administered NGF on the olfactory cholinergic circuit supported the hypothesis that the projection from the HDB to the OB is a neuronal pathway for which NGF might be a neurotrophic factor.