The hindlimb hyperextension associated to the urogenital response in newborn underfed rats

The aim of the study was to investigate how neonatal undernutrition interacts with mother-infant relationships to interfere with the expression of the urogenital response in the newborn.

The hyperextensive reflex components associated to the urogenital response (HUR) were measured between postnatal days 1-21, in control and neonatally undernourished rats with or without fullness of the bladder.

In Experiment 1, both male and female underfed rats with different degrees of bladder fullness exhibited an increment in HUR latency and vertical hindlimb displacement, reduced transversal separation and prolonged performance of hindlimb relaxation. Experiment 2 was performed in rats after urine elicitation provoked only reduced hindlimb transversal separation in males, and prolonged latency to HUR in females.

These findings may be related to the vulnerability to neonatal undernutrition of the maturational processes which take place in the spinal cord, the condition of the bladder, and hindleg muscle maturation during this period of life.

Data suggest that neonatal undernutrition may play a role in mother-infant interaction by interfering with HUR responses to maternal anogenital licking of the pups.