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Published on: February 2, 2024
Exposure to Altered Gravity During Specific Developmental Periods Differentially Affects Growth, Development, the
Insights
Neonatal cerebellar development and motor skills are vulnerable to hypergravity during specific windows. The postnatal period is most sensitive, but males show mid-pregnancy vulnerability.
Area of Science:
- Neuroscience
- Developmental Biology
- Gravitational Biology
Background:
- Perinatal hypergravity exposure impacts cerebellar structure and motor coordination in rat neonates.
- Specific developmental stages may present heightened vulnerability to hypergravity's effects.
Purpose of the Study:
- To determine critical developmental windows of vulnerability for the neonatal cerebellum and motor behavior under hypergravity.
- To investigate potential sex-dimorphic responses to hypergravity during development.
Main Methods:
- Rat neonates were exposed to 1.65 G during distinct gestational and postnatal periods.
- Neurodevelopment, motor behavior (righting reflex, startle response, rotarod performance), and cerebellar structure were assessed.
- Comparisons were made between hypergravity-exposed groups and stationary controls.
Main Results:
- Prenatal hypergravity caused intrauterine growth retardation.
- Postnatal exposure impaired righting and startle responses, with peak effects in the second and third weeks after birth.
- Rotarod performance was impaired by postnatal exposure, with males most affected by mid-gestational exposure.
- Cerebellar mass reduction was most pronounced with later postnatal exposure.
Conclusions:
- The postnatal period, coinciding with the brain growth spurt, is the most vulnerable for cerebellar development under hypergravity.
- Male motor behavior exhibits vulnerability to mid-pregnancy hypergravity, indicating sexually dimorphic windows of CNS sensitivity to environmental stress.
Abstract:
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.
