Cytomorphometric Changes in Hippocampal CA1 Neurons Exposed to Simulated Microgravity Using Rats as Model

Abstract

Microgravity and sleep loss lead to cognitive and learning deficits. These behavioral alterations are likely to be associated with cytomorphological changes and loss of neurons. To understand the phenomenon, we exposed rats (225–275 g) to 14 days simulated microgravity (SMg) and compared its effects on CA1 hippocampal neuronal plasticity, with that of normal cage control rats. We observed that the mean area, perimeter, synaptic cleft, and length of active zone of CA1 hippocampal neurons significantly decreased while dendritic arborization and number of spines significantly increased in SMg group as compared with controls. The mean thickness of the postsynaptic density and total dendritic length remained unaltered. The changes may be a compensatory effect induced by exposure to microgravity; however, the effects may be transient or permanent, which need further study. These findings may be useful for designing effective prevention for those, including the astronauts, exposed to microgravity. Further, subject to confirmation, we propose that SMg exposure might be useful for recovery of stroke patients.

Effects of simulated microgravity on the expression of presynaptic proteins distorting the GABA/glutamate equilibrium – A proteomics approach

“…The long‐term exposure to SM also decreased syntaxin‐1A. It is part of the SNARE complex formation in membrane fusion in the neuronal exocytosis of SVs . Previous studies revealed that syntaxin‐1A is present in open and closed forms.…”

“…Microgravity‐induced cognitive deficits are associated with cytomorphological changes and loss of hippocampus CA 1 neurons within 14 days SM . The hippocampus is a vital brain region for memory storage and retrieval .…”

Neonatal exposure to benzo[a]pyrene induces oxidative stress causing altered hippocampal cytomorphometry and behavior during early adolescence period of male Wistar rats

“…The identification of neurons and glia were carried out as suggested previously (Garman, 2011). The neuronal and glial cells in hippocampus of naïve, control and B[a]P groups were counted in dissecting microscope (Ranjan et al, 2014). The area and perimeter of the whole hippocampus, neuron and neuronal nucleus were measured with the help of ocular micrometer at 120× magnification.…”

The effects of simulated microgravity on the human nervous system: the proposal of a three-dimensional glia–neuron co-culture cell model

“…Treatment in simulated microgravity has revealed only increases in glial fibrillary acidic protein fluorescence in elongated stellate glial cells [13] . In contrast with these findings, Ranjan and colleagues (2014) observed that in rats exposed to simulated microgravity, some areas of the active zone of CA1 hippocampal neurons significantly decreased, while dendritic arborization and the number of spines significantly increased [18] .…”