Simulated dive in rats lead to acute changes in cerebral blood flow on MRI, but no cerebral injuries to grey or white matter

Abstract

In this study, the effect of a simulated dive on rat brain was investigated using several magnetic resonance imaging (MRI)-methods and immunohistochemistry. Rats were randomly assigned to a dive- or a control group. The dive group was exposed to a simulated air dive to 600 kPa for 45 min. Pulmonary artery was monitored for vascular gas bubbles by ultrasound. MRI was performed 1 h after decompression and at one and 2 weeks after the dive with a different combination of MRI sequences at each time point. Two weeks after decompression, rats were sacrificed and brains were prepared for histology. Dived rats had a different time-curve for the dynamic contrast-enhanced MRI signal than controls with higher relative signal intensity, a tendency towards longer time to peak and a larger area under the curve for the whole brain on the acute MRI scan. On MRI, 1 and 2 weeks after dive, T2-maps showed no signal abnormalities or morphological changes. However, region of interest based measurements of T2 showed higher T2 in the brain stem among decompressed animals than controls after one and 2 weeks. Microscopical examination including immunohistochemistry did not reveal apparent structural or cellular injuries in any part of the rat brains. These observations indicate that severe decompression does not seem to cause any structural or cellular injury to the brain tissue of the rat, but may cause circulatory changes in the brain perfusion in the acute phase.

Unexpected Terrain Induced Changes in Cortical Activity in Bipedal-Walking Rats

“…The experiments were conducted on six male Sprague Dawley (SD) rats [ 33 ] weighing 250–300 g. SD rats were widely used in behavior and neuroscience studies due to their docile nature, strong adaptability, and excellent reproductive performance [ 34 , 35 , 36 , 37 ]. Each rat was individually maintained in a plexiglass cage with 12 h light/12 h dark cycles.…”

A biophysical vascular bubble model for devising decompression procedures

“…It is therefore possible that whereas cerebral circulation following a dive may increase (Havnes et al. ), the reduction in spinal arterial blood flow could enhance the formation of arterial bubbles in the spinal cord (Fig. ).…”

Fast hyperbaric decompression after heliox saturation altered the brain proteome in rats

“…Previous experiments in our laboratory has shown that decompression from heliox saturation at a rate of 1 bar/20 s (fast), resulted in DCS symptoms in approximately 50% of the animals, whereas the slow rate of 1 bar/10 min did not result in DCS or venous gas bubbles [ 14 , 15 ]. Structural MRI did not reveal morphological changes in CNS in rats with severe bubble formation and DCS symptoms after air and heliox dives [ 14 , 16 ]. However, from functional MRI, Havnes et al (2013) concluded that circulatory changes might occur in the brain during the acute phase [ 16 ].…”

“…Structural MRI did not reveal morphological changes in CNS in rats with severe bubble formation and DCS symptoms after air and heliox dives [ 14 , 16 ]. However, from functional MRI, Havnes et al (2013) concluded that circulatory changes might occur in the brain during the acute phase [ 16 ]. Increased serum levels of the protein biomarker S100B, predominantly found in brain glial cells, have been associated with brain injury [ 17 ].…”