Effects of Hypergravity Exposure on the Developing Central Nervous System: Possible Involvement of Thyroid Hormone

Advances in Space Research

2006

We previously reported that perinatal exposure to hypergravity affects cerebellar structure and motor coordination in rat neonates. In the present study, we explored the hypothesis that neonatal cerebellar structure and motor coordination may be particularly vulnerable to the effects of hypergravity during specific developmental stages. To test this hypothesis, we compared neurodevelopment, motor behavior and cerebellar structure in rat neonates exposed to 1.65 G on a 24-ft centrifuge during discrete periods of time: the 2 nd week of pregnancy [gestational day (G) 8 through G15; group A], the 3 rd week of pregnancy (G15 through birth on G22/G23; group B), the 1 st week of nursing [birth through postnatal day (P) 6; group C], the 2 nd and 3 rd weeks of nursing (P6 through P21; group D), the combined 2 nd and 3 rd weeks of pregnancy and nursing (G8 through P21; group E) and stationary control (SC) neonates (group F). Prenatal exposure to hypergravity resulted in intrauterine growth retardation as reflected by a decrease in the number of pups in a litter and lower average mass at birth. Exposure to hypergravity immediately after birth impaired the righting response on P3, while the startle response in both males and females was most affected by exposure during the 2 nd and 3 rd weeks after birth. Hypergravity exposure also impaired motor functions, as evidenced by poorer performance on a rotarod; while both males and females exposed to hypergravity during the 2 nd and 3 rd weeks after birth performed poorly on P21, male neonates were most dramatically affected by exposure to hypergravity during the second week of gestation, when the duration of their recorded stay on the rotarod was one half that of SC males. Cerebellar mass was most reduced by later postnatal exposure. Thus, for the developing rat cerebellum, the postnatal period that overlaps the brain growth spurt is the most vulnerable to hypergravity. However, male motor behavior is also affected by midpregnancy exposure to hypergravity, suggesting discrete and sexually dimorphic windows of vulnerability of the developing central nervous system to environmental perturbations.

Section: Introductionmentioning

confidence: 87%

Exposure to altered gravity during specific developmental periods differentially affects growth, development, the cerebellum and motor functions in male and female rats

Nguon

Ladd

Advances in Space Research

2006

“…Results of these studies have shown that exposure to hypergravity (1.5 G) during the perinatal period, including the critical brain development period (P5-P10), affects both the pregnant dams (Ladd et al 2006) and neonates (Sajdel-Sulkowska et al 2001). Pregnant rat dams exposed to hypergravity show lower food consumption, lower weight gain, and altered pregnancy outcome.…”

Section: Cerebellar Development Under Altered Gravitymentioning

confidence: 98%

Cerebellum and Gravity: Altered Earth’s Gravity Perception Under Pathological Conditions and Response to Altered Gravity in Space

Handbook of the Cerebellum and Cerebellar Disorders

2013

Self Cite

Life on Earth has developed under the influence of gravity and remains adapted to unit gravity. As different organisms evolved to survive optimally in water, ground, and air habitats, special adaptive mechanisms developed to deal with gravity. In humans and most land mammals, maintaining postural equilibrium requires constant integration of visual, vestibular, and somatosensory systems to compensate for gravity. The gravity sensors located in the inner ear make connections to the eyes, vestibulocerebellum, and postural muscles. The vestibulocerebellum, due to direct connections with the vestibular gravity receptors, is the primary gravity response center. It is involved in spatial orientation and regulation of gait and, together with the spinocerebellum and pontocerebellum, plays an important role in motor control. Several cerebellar pathologies, including ataxias and dystonia in humans and animals, are characterized by altered gravity perception and affect posture, gait, and small motor coordination and timing. In space, where the gravitational sense of up and down diminishes, the vestibulocerebellar system must adapt and establish a new way to interpret the altered gravitational environment. This chapter explores cerebellar disorders in the context of altered interactions with Earth's gravity in humans and animal models and the reaction of astronauts to altered gravity in space (microgravity). This chapter also considers the effects of microgravity and

“…Results of our studies have indicated that the mass of the forebrain and the mass of the cerebellum were maximally reduced on P6 by 15.9% and 25.6% respectively. The results of three way ANOVA, with gravitational condition, age and either body, forebrain or cerebellar mass as a factor suggested that the effect of hypergravity on the CNS is independent of the effect on body mass and that the changes in the forebrain and the cerebellum are independent of each other (19). Results of our studies also suggest a biphasic nature of changes in the cerebellum, with the first downward deviation from control in cerebellar mass between P6 and P9 and a second around P21.…”

Section: Gravireaction To Hypergravitymentioning

confidence: 92%

“…This is suggested by observations that prenatal exposure of rats to microgravity affects the righting response (15) and motor and equilibrium behavior that are associated with structural changes in the brain (16). Cerebellar abnormalities are frequently associated with deficits in motor functions (17) and cerebellar abnormalities have been observed both under microgravity and hypergravity (18)(19)(20)(21)(22)(23)(24)(25).…”

Section: Gravireaction Of the Mature Cnsmentioning

confidence: 99%

“…Another system employs hypergravity (27)(28), which can be generated on a centrifuge (29). In particular, the large-radius centrifuge at Ames Research Center provides an ideal system to perform large-scale and long-term developmental studies (19)(20)(21)(22)(23)(24)(25). Serova (30) compared the effects of microgravity and 2G hypergravity on various developmental phases of rats; she concluded that hypergravity is a good model to evaluate the potential effect of reduced gravity during space flights.…”

Section: Gravireaction Of Cns Developing Under Altered Gravitymentioning

confidence: 99%

See 1 more Smart Citation

Brain development, environment and sex: what can we learn from studying graviperception, gravitransduction and the gravireaction of the developing CNS to altered gravity?

2008

Cerebellum

Self Cite

As man embarks on space exploration and contemplates space habitation, there is a critical need for basic understanding of the impact of the environmental factors of space, and in particular gravity, on human survival, health, reproduction and development. This review summarizes our present knowledge on the effect of altered gravity on the developing CNS with respect to the response of the developing CNS to altered gravity (gravireaction), the physiological changes associated with altered gravity that could contribute to this effect (gravitransduction), and the possible mechanisms involved in the detection of altered gravity (graviperception). Some of these findings transcend gravitational research and are relevant to our understanding of the impact of environmental factors on CNS development on Earth.