ABSTRACT
This study investigated the effects of repeated l-arginine administration during lactation, combined with different suckling conditions, on morphometric parameters of primary visual cortex NADPH-diaphorase-positive neurons. Wistar rat pups reared in "normal-size litters" or "large litters" (N- and L-conditions; litters formed by 6 and 12 pups, respectively) received, from postnatal day 7 to 28, either arginine (300 mg/kg/day, per gavage) or distilled water (control). At 90-120 days of life, they were perfused with saline + formaldehyde, and their brains were processed for histochemical reaction to reveal NADPH-diaphorase-positive neurons (malic enzyme indirect method). Compared to the normal-size litters, L-rats had lower body weights (P < 0.05), confirming the effectiveness of the L-condition in affecting pup development. Concerning NADPH-d histochemistry, arginine treatment was associated with increased (P < 0.05) density of dendrite varicosities and of dendrite branching frequency, suggesting a plastic response of the developing brain to that treatment, even in previously malnourished rats. No difference was seen, however, in dendrite orientation, total number of neurons, soma area and perimeter, as well as dendrite bifurcation points, fractal dimension, and area and volume of dendrite field, suggesting that NADPH-d cells are resistant to arginine and nutritional changes, regarding these features. Data are considered of interest for studies of synaptic plasticity during neural development and its relationships to aggressive agents like malnutrition.
