Cerebellar Afferents to Neuroendocrine Cells: Implications for Adaptive Responses to Simulated Weightlessness.

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: Discussionmentioning

confidence: 99%

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

“…A review by Katafuchi et al (1995) provides evidence of a neurophysiological response to altered gravity in animals. These responses are associated with metabolic and neurochemical changes Sirota et al 1987;Miller et al 1989;Grindeland et al 1990;Fareh et al 1993).…”

Section: Effect Of Altered Gravity On the Cerebellum In Animalsmentioning

confidence: 99%

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

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

“…Because up to 70% of astronauts experience some form of motion sickness and disturbances in motor coordination and movement (6), most of the animal studies to date have targeted the response of the peripheral vestibular system to altered gravity (7). A number of ground-based experiments employing hypergravity generated in a large-radius horizontal centrifuge (8) have suggested that hypergravity is a good model to evaluate potential effects of reduced gravity during space flights.…”

mentioning

confidence: 99%

“…Altered function of the vestibular system has been observed in adult rats (9) and hamsters raised under hypergravity (10). Since even a short exposure to altered gravity encountered by astronauts (6) or adult animals (7,8) affects CNS function, prolonged exposure to altered gravity during embryonic and early neonatal development is ex-pected to have much more dramatic and long-lasting consequences. As the possibility of long-term space travel and habitation is becoming a reality, understanding the development of the CNS under microgravity is increasingly important.…”

mentioning

confidence: 99%

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

Ronca

et al. 2001

Exp Biol Med (Maywood)

The present study examined the effects of hypergravity exposure on the developing brain and specifically explored the possibility that these effects are mediated by altered thyroid status. Thirty-four timed-pregnant Sprague-Dawley rats were exposed to continuous centrifugation at 1.5 G (HG) from gestational Day 11 until one of three key developmental points: postnatal Day (P) 6, P15, or P21 (10 pups/dam: 5 males/5 females). During the 32-day centrifugation, stationary controls (SC, n = 25 dams) were housed In the same room as HG animals. Neonatal body, forebrain, and cerebellum mass and neonatal and maternal thyroid status were assessed at each time point. The body mass of centrifuged neonates was comparatively lower at each time point. The mass of the forebrain and the mass of the cerebellum were maximally reduced In hypergravlty-exposed neonates at P6 by 15.9% and 25.6%, respectively. Analysis of neonatal plasma suggested a transient hypothyroid status, as indicated by Increased thyroid stimulating hormone (TSH) level (38.6%)at P6, while maternal plasma TSH levels were maximally elevated at P15 (38.9%). Neither neonatal nor maternal plasma TH levels were altered, suggesting a moderate hypothyroid condition. Thus, continuous exposure of the developing rats to hypergrav-Ity during the embryonic and neonatal periods has a highly significant effect on the developing forebrain and cerebellum and neonatal thyroid status (P < 0.05, Sonferronl corrected). These data are consistent with the hypothesized role of the thyroid hormone In mediating the effect of hypergravity In the developing central nervous system and begin to define the role