UNDERNUTRITION DURING EARLY-LIFE DOES NOT AFFECT THE NUMBER OF GRANULE CELLS IN THE RAT OLFACTORY-BULB

Undernutrition during early life causes deficits and distortions of br ain structure. However, whether or not this includes a diminution of t he total numbers of neurones remains uncertain. Recent advances in ste reological techniques have made it possible to obtain unbiased estimat es of total numbers of cells in well-defined biological structures. Ra ts were undernourished from conception to 90 postnatal days of age by standardised procedures. Groups of well-fed control and undernourished rats were anaesthetised and killed by intracardiac perfusion with fix atives at 30 and 90 days of age. Each olfactory bulb was serially sect ioned at a nominal thickness of 100 mu m on a vibratome. These section s were analysed by the Cavalieri principle to obtain estimates of the total volume of the olfactory bulb as well as the volume of its granul e cell layer. The physical ''disector'' method was later used on seria l 1-mu m-thick toluidine-blue-stained sections to estimate the numeric al density of granule cell neurones in the olfactory granule cell laye r. These values were used to compute estimates of the total number of olfactory granule cell neurones for each animal. Thirty-day-old contro l and undernourished rats had between 2.6 and 3 million granule cell n eurones in the olfactory bulb. By 90 days of age the number of granule cells had increased in both groups of animals to between about 4.2 an d 5.2 million cells. Analysis of variance tests showed a significant m ain effect of age but not nutrition in these estimates. Although the i nteraction term did reach statistical significance, post hoc analysis did not reveal any differential effect of undernutrition between the t wo age groups examined. Therefore, undernutrition of rats from concept ion until 90 postnatal days of age does not seem to affect the total n umbers of granule cell neurones in the olfactory bulbs. (C) 1994 Wiley -Liss, Inc.