Is the maturation of monosynaptic stretch reflex in rats affected by neonatal malnutrition?

We compared the maturation of the monosynaptic stretch reflex in control rats and in rats submitted to neonatal malnutrition. Electrical stimulations of the sciatic nerve were applied in wakeful rats of different ages (21-90 days) to record, by surface electrodes, the maximal direct motor response (M(max)) or the maximal Hoffmann reflex (H(max)). Percussion on the Achilles tendon induced the T-reflex. Animals submitted to neonatal malnutrition showed significant reductions in H-reflex latency and in velocity index of nervous conduction. The H- or T-reflex amplitudes were lower for malnourished rats of 21 days but the difference was significant only for the T(max)/M(max) ratios. The reflexes evoked at older ages did not present differences between control and malnourished rats. In conclusion, rats submitted to neonatal malnutrition present long-term alteration in reflex latency and nervous conduction velocity. Neonatal malnutrition also alters the reflex excitability at weaning but, since the rat were submitted to a normal diet after weaning, a normal reflex excitability was rapidly recovered which indicates a remarkable plasticity of the reflex pathway.