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Hindlimb Suspension As A Model For Intracranial And Intraocular Pressures, And Retinal Changes During Spaceflight
Author(s) -
Fuller Charles A,
Gompf Heinrich,
HobanHiggins Tana,
Robinson Edward
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.711.3
Subject(s) - spaceflight , medicine , intraocular pressure , intracranial pressure , physiology , anesthesia , surgery , engineering , aerospace engineering
A pronounced cephalic fluid shift is one of the responses to exposure to the microgravity spaceflight environment. This project uses the well‐documented rat hindlimb suspension (HLS) model to test the hypothesis that this fluid shift is a causative factor underlying the ocular changes seen in astronauts during and following long‐duration spaceflight. This hypothesis follows from the fact that similar ocular effects are seen in Idiopathic Intracranial Hypertension (IIH) and are associated with increased intraocular pressure (IOP). In order to elucidate the roles played by age and sex in the relationship between a cephalic fluid shift and the regulation of intracranial pressure (ICP) and IOP, as well as visual system structure and function, three cohorts are under study: young adult females, young adult males, and older middle‐age males. Groups of animals are exposed to HLS durations of 0 (baseline), 7, 14, 28 and 90 days with 90 days of HLS being followed by equivalent intervals of recovery in a vivarium cage, i.e. either 0, 7, 14, 28 or 90 days. Each HLS subject has an age‐matched control maintained in the same room but in a vivarium cage. An LD 12:12 cycle is present and all subjects have ad lib access to food and water. This presentation represents a status report of this ongoing program. We have measured ICP in one group of subjects. ICP recording is underway for the other 2 groups. To date, the data identify a very small increase in ICP, which is maintained during HLS. Our hypothesis is that this increase in ICP could lead to morphological changes in visual structures similar to those seen previously in some astronauts following long duration missions. To this end, MRI was used to image the eyes and brains in all 3 groups at baseline and at the midpoint and endpoint of HLS and recovery. Data analysis indicates increased optic nerve sheath diameters which are most pronounced in the middle‐aged males yet also observed in younger males, as well as globe flattening in HLS. IOP continues to be measured in all animals under study. In general, there is a trend for increased IOP during HLS. Moreover, refractive error increases over 90 days of suspension. These preliminary results continue to be supportive of our hypothesis that an increase in ICP may underlie such ocular changes. Support or Funding Information Supported by NASA Grant NNX13AD94G.