Effects of fetal exposure to lipopolysaccharide, perinatal anoxia and sensorimotor restriction on motor skills and musculoskeletal tissue: implications for an animal model of cerebral palsy.

Cerebral palsy (CP) is a disorder of locomotion, posture and movement that can be caused by prenatal, perinatal or postnatal insults during brain development. An increased incidence of CP has been correlated to perinatal asphyxia and maternal infections during gestation. The effects of maternal exposure to low doses of bacterial endotoxin (lipopolysaccharide, LPS) on motor behavior and hind leg muscle morphology were examined in young adult rats. Prenatal exposure to LPS was also studied in association with perinatal anoxia (PA) and/or combined with subsequent sensorimotor restriction (SR) and all possible combinations of the three conditions. Rats exposed to LPS, PA and SR alone or combined (LPS + PA, LPS + SR, PA + SR, and LPS + PA + SR) showed deficits in balance and coordination when tested on the Rotarod. The SR groups, with or without other insults, (SR, LPS + SR, PA + SR, and LPS + PA + SR) exhibited the greatest motor deficits, characterized by the reduced ability to perform the horizontal ladder and suspended bar tests on postnatal day 29 (P29) and P45. Histological assessment revealed substantial morphological alterations in the slow ankle extensor soleus muscle of all SR rats. Soleus myofibers presented a reduction in cross-sectional area (CSA), an increase in sarcomere length and a decrease in sarcomere density. The CSA of the fast flexor tibialis anterior muscle was only decreased by the association of all treatments (LPS, PA, SR), but no differences were found in sarcomere length and density when compared to control. A slow-to-fast fiber type transition was only observed in the soleus and tibialis anterior muscles in the SR groups. These results suggest that exposure to LPS during the prenatal period, PA, SR alone or in combination has various degrees of consequences on motor behavior and muscle morphology. These data corroborate the concept that early experience-dependent movements play the most important role in shaping motor behavior and that reduced or anomalous sensorimotor experience can contribute to the development of aberrant motor behavior and muscle morphology.