Comparison of the effects of spaceflight and hindlimb-suspension on rat pituitary vasopressin and brainstem norepinephrine content.
To compare actual spaceflight to ground-based simulation (hindlimb-suspension), we measured the norepinephrine (NE) content in A1, A2, A5 and A6 (locus coeruleus) and the vasopressin content in the neurohypophysial system.  The experimental period was of 9 days' duration.  The NE content in the locus coeruleus decreased significantly in rats flown for 9 days (67%, p < 0.001), but showed no significant changes after hindlimb-suspension.  These results demonstrated that suspended rats adapted better to weightlessness-simulation than flown rats to actual microgravity.  In rats flown aboard SLS-1, the vasopressin content was significantly increased in the posterior pituitary (71%, p < 0.01), and was decreased in the hypothalamus (49%, p < 0.05).  In 9-day suspended rats pituitary vasopressin levels were unchanged, while in the hypothalamus a significant decrease was noted (21%, p < 0.05).  It was concluded that spaceflight changes in pituitary vasopressin levels and in the locus coeruleus NE content were consistent with a stress reaction, occurring during and/or after landing.  These results confirmed that hindlimb-suspension model constitutes a valid and less stressful [correction of lesstressful] ground-based simulation of microgravity in rats.
Fareh
J
J
Laboratoire de Physiologie de l'Environnement, Lyon Grange-Blanch, Lyon, France.
Fagette
S
S
Cottet-Emard
J M
JM
Allevard
A M
AM
Viso
M
M
Gauquelin
G
G
Gharib
C
C
D000818:Animals; D001923:Brain Chemistry; D001933:Brain Stem / Q000737:chemistry; D006614:Hindlimb; D007031:Hypothalamus / Q000737:chemistry; D007103:Immobilization; D008125:Locus Coeruleus / Q000737:chemistry; D008297:Male; D009638:Norepinephrine / Q000032:analysis*; D010902:Pituitary Gland / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013026:Space Flight; D014667:Vasopressins / Q000032:analysis*; D014893:Weightlessness; D018474:Weightlessness Simulation
D014667:Vasopressins; D009638:Norepinephrine