Lasting effects of early olfactory deprivation on the growth, DNA, RNA and protein content, and Na-K-ATPase and AChE activity of the rat olfactory bulb

Abstract

It is shown that when one of the olfactory bulbs (OB) of the rat is deprived of olfactory stimulation from birth, as compared to the normal OB on the opposite side, significant and permanent reductions in its growth and in several biochemical parameters take place as follows: weight gain, 25%; total DNA, 20–30%; total RNA, 30%; total protein, 30%; total Na-K-ATPase activity, 50%; total AChE activity, 20%. The concentrations of DNA, RNA and protein and the specific activity of AChE were not significantly affected but the specific activity of Na-K-ATPase was significantly reduced. In general, these interbulbar differences were seen in every experimental animal and were not due to hypertrophy or hyperplasia of the normal OB. These results suggest that olfactory stimulation during the early postnatal period has a significant influence on cell proliferation and cell growth as well as on the proliferation of neuronal membranes and synapses in the developing OB. It appears that the effects of olfactory deprivation are exerted during the first few weeks after birth when the bulb shows its most rapid period of growth and development, since (with the exception of DNA) the magnitude of the interbulbar difference did not increase appreciably by prolongation of olfactory deprivation beyond the early period. Thus in the rat the existence of a critical period encompassing the second and third postnatal weeks is suggested during which the developing OB appears to be especially vulnerable to the absence of olfactory stimulation.