Neuromotor Development in Relation to Birth Weight in Rabbits

Abstract

The development of neuromotor patterns in relation to birth weight was studied in the rabbit, a perinatal brain developer. In order to induce intrauterine growth retardation and to increase the number of low birth weight rabbits, experimental ischemia to half the fetuses in each doe was achieved by total ligation of approximately 30% of spiral vessels to the placenta, during the last trimester of gestation. Following natural delivery, the rabbit pups were periodically observed for the appearance of eye-opening and righting reflex, and for the cessations of falling, circling and dragging of hind limbs. An index of neuromotor development was assigned to each rabbit by summing up the age (in days) of appearance of each of the neuromotor milestones. An association was found between low birth weight and delayed neuromotor development at 2 weeks of age. The most significant correlation was found between low birth weight and delayed disappearance of falling. The latter may represent incoordination as an expression of cerebellar dysfunction.

Local Cerebral Blood Flow in the Newborn Rabbit: An Autoradiographic Study of Changes during Development

“…Electrophysiologic experiments have shown that the action potentials recorded from predominantly thalamic cells in urethane-anesthetized rabbits increase their frequency of firing at 14 d, attain adult levels at 30 d, and exceed adult levels at 70 d of age (44). Behaviorally, the rabbit has poor walking and righting skills, which mature within the first 14 d. Between 14 and 21 d of age, the rabbit commences hopping with all locomotion subsequently converting to hopping (45). Eye opening occurs between d 8 and 14, weaning at approximately 40 d, and puberty at approximately 80 d (44,45).…”

“…Behaviorally, the rabbit has poor walking and righting skills, which mature within the first 14 d. Between 14 and 21 d of age, the rabbit commences hopping with all locomotion subsequently converting to hopping (45). Eye opening occurs between d 8 and 14, weaning at approximately 40 d, and puberty at approximately 80 d (44,45). Thus, in the rabbit, the marked increases in cerebral blood flow observed between 8 and 17 d of age occur at a time of marked maturational advances in anatomy, electrophysiology, and behavior.…”

The effects of vascular intrauterine growth retardation on cortical astrocytes

“…By visual estimation, 25% of uteroplacental spiral vessels to each placenta were permanently ligated with silk sutures. The embryos on the other uterine horn served as physiologic control [19]. The uterine horns were then returned to the abdominal cavity, and muscle and skin tissues were closed with a single stitch each.…”

“…In the current study, we sought to induce mild fetal ischemia in rabbit fetuses by utilizing a partial uteroplacental vascular-ligation IUGR model [19]. We hypothesized that mild intrauterine ischemia during the end of the third trimester of pregnancy will be enough to alter the ongoing cortical astrocytogenesis, specifically, astrocytic proliferation, migration to the upper cortical layers, and maturation [20].…”

Vascular Placental Insufficiency in the Rabbit

“…The present study is part of a series of experiments aimed at examining the effect of experimentally induced vascular IUGR on various aspects of brain development includ ing: fetal and neonatal brain biochemistry [9], muscarinic receptors [10, 11], brain/body ra tio (cephalization index) [12,13], learning ability [14], and neuromotor skills [15], Isch emic conditions are also known to affect pros taglandins and other arachidonic acid de rived metabolites [16][17][18].…”