Substance P effects on developing thymocytes in hindlimb unloaded rats.

Introduction: The purpose of this study was to examine the effects of substance P (SP) on the immune system in a condition similar to microgravity. We analyzed immune disturbances caused by subjecting Fischer 344 rats to a 45 degrees antiorthostatic suspension technique, otherwise known as the hindlimb unloading (HU) model.

Methods: Four groups of rats were assigned to either the prone control non-substance P group (P-NSP), prone control substance P group (P-SP), hindlimb unloaded non-substance P (HU-NSP) or the hindlimb unloaded substance P group (HU-SP).

Changes in organ perfusion and weight ratios in post-simulated microgravity recovery.

Head-down tilt models have been used as ground-based simulations of microgravity. Our previous animal research has demonstrated that there are significant changes in fluid distribution within 2 h after placement in a 45 degrees head-down tilt (45HDT) position and these changes in fluid distribution were still present after 14 days of 45HDT. Consequently, we investigated changes in fluid distribution during recovery from 16 days of 45HDT.