E 33 LOW PRESSURE HYPERBARIC OXYGEN THERAPY ( LPHBOT ) INDUCES CEREBROVASCULAR CHANGES AND IMPROVES COGNITIVE FUNCTION IN A RAT TRAUMATIC BRAIN INJURY (TBI) MODEL.
PJ Hatch, CL Kriedt, MP Weisend, KW Van Meter, R.I Sutherland, Baromedical Research Institute & LSU School of Medicine, New Orleans, LA 70114, and University of New Mexico Depts. of Psychology and Physiology, Albuquerqui, NM 87131

INTRODUCTION: In 1996 pilot data were reported on this project [UHM, 1996, 23: (Suppl); 48]. The present study ia a replication of the cognitive improvements and blood vessel changes in that experiment using a larger number of rats.

METHODS: 42 adult male Long-Evans hooded rats were subjected to the unilateral weight-drop focal cortical impact model of TBI. 49 days following TBI, the ram underwent LPHBOT in 2 groups: (1) 80 bid 13 ATA/90 HBOTs (n=l 9); (2) 80 bid sham air treatments (n=23). Motor function and spatial memory tasks were assessed before and after HBOT. Animals were sacrificed, brains sectioned, stained with T,T-diaminobenzidine, and vessel density analyzed via computer assisted densitometry.
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RESULTS: LPHBOT increased hippocampal vessel density ratio (injured/uninjured hemisphere). The increased ratio was due to a decrease in the contralateral vessel density with HBOT (p<0.01). Using an ANCOVA procedure, we found that HBOT significantly improved spatial memory in the Morris water task IF(l,41)=7.34, p<0.01], but not motor function, as measured by forelimb placing contralateral to the contusion. Hippocampal vessel density ratio positively correlated with Morris water task improvement (R=0.68, p<0.001). No correlation was found between cortical vessel density and forelimb placing tasks.

CONCLUSION: LPHBOT induced improvement in spatial memory, but not motor function, and induced cerebrovascular changes in a rat model of chronic TBL To our knowledge this is the only demonstration of improvement in chronic brain injury in an animal model.