Ultrastructural Alterations in the Sensorimotor Cortex upon Delayed Development of Motor Behavior in Early Ontogenesis of Rats Exposed to Prenatal Hypoxia

Abstract

A comparative study of morphogenesis and synaptogenesis of the sensorimotor cortex and changes in motor behavior during early ontogenesis (Р5, Р14) of rats with normal development and rats subjected to prenatal hypoxia at Е14 (7% O2, 3 h) has been performed. The rats subjected to prenatal hypoxia exhibited delayed maturation of neural elements of the sensorimotor cortex in the first 2 weeks of postnatal ontogenesis. The following signs of nervous tissue immaturity were revealed in the neuropil of the sensorimotor cortex: a large volume of extracellular space, multiple growth cones, insufficient neuronal differentiation, lack of mature synapses, single spines without spine apparatus, and contacts between processes in the form of desmosomes. In addition to delayed formation of neural elements, 14-day-old rats subjected to prenatal hypoxia had signs of nerve cell destruction: hyperchromatosis, chromatolysis with organelle lysis, and destruction of the outer membrane. Prenatal hypoxia is a severe stress factor and has been shown to cause delayed development of motor activity in rat pups in early ontogenesis, such as a delayed reaction of forelimb placing on the surface and reduced total spontaneous motor activity. A comparison of the results with previous data on similar changes in the dorsolateral striatum leads to the conclusion that the action of the adverse factor during embryogenesis causes morphological and functional delay in formation of corticostriatal system elements, leading to impaired development of motor behavior and disturbance of coordinated responses in animals.