Fetal Patterns of Interlimb Movement Synchrony, Facial Wiping, and Nipple Attachment are Altered by Prenatal Exposure to Methylazoxymethanol (MAM)

Abstract

There is considerable interest in the early detection of neuromotor deficits, including disorders that may be the result of toxin exposure during early development. Until recently, quantifiable methods for determining the immediate developmental effects of prenatal toxin exposure have been unavailable. However, several behavioral measures employed in this lab have shown clear prenatal patterns of development, suggesting their possible utility in detecting early assaults to the CNS. To test this hypothesis, pregnant rats were injected with the neurotoxin methyazoxymethanol (MAM, Midwest Research Inst.) on E17 of gestation. Fetuses then were prepared for in vivo behavioral observation 72 hours later, on E20, to measure: (a) interlimb movement synchrony between different pairwise limb combinations during spontaneous movement, (b) facial wiping response to intraoral lemon infusion, which requires coordination between forepaws and face, and (c) presentation of an artificial nipple, which evokes oral grasping responses in fetal rats. Although MAM-treated subjects did not differ from saline controls in overall appearance and weight, clear disruptions of movement coordination were seen in all three behavioral measures. These results suggest that these quantifiable behavioral measures may be useful in the prenatal assessment of CNS deficits. Supported by grant HD 33862 to SRR