CHRONIC ORTHOSTATIC AND ANTIORTHOSTATIC RESTRAINT INDUCE NEUROENDOCRINE, IMMUNE AND NEUROPHYSIOLOGICAL DISORDERS IN RATS

Citation
I. Assenmacher et al., CHRONIC ORTHOSTATIC AND ANTIORTHOSTATIC RESTRAINT INDUCE NEUROENDOCRINE, IMMUNE AND NEUROPHYSIOLOGICAL DISORDERS IN RATS, Acta astronautica, 36(8-12), 1995, pp. 545-558
Citations number
26
Categorie Soggetti
Aerospace Engineering & Tecnology
Journal title
ISSN journal
00945765
Volume
36
Issue
8-12
Year of publication
1995
Pages
545 - 558
Database
ISI
SICI code
0094-5765(1995)36:8-12<545:COAARI>2.0.ZU;2-0
Abstract
The tail-cast suspension rat model has been developed in ground labora tories interested in space physiology for extensive study of mechanism s causing the pathophysiological syndrome associated with space flight s, We used individually-caged male rats to explore the effects of acut e and chronic (7d) orthostatic restraint (OR) and head-down anti-ortho static restraint (AOR) on a series of physiological variables; The acu te restraint study showed that (1) the installation of the OR device i nduced an acute reaction for 2 days, with a substantial rise in ACTH ( x2) and CORT (x6), and that (2) the head-down tilt from OR to AOR indu ced (i) within 10 min and lasting 60 min a 2-fold rise in the intra-ce rebro-ventricular pressure (Picv) monitored with an icy telemetric rec ording system, which receded to normal between 60 and 120 min; and (ii ) within 30 min a short-lived 4-fold rise in plasma ACTH and CORT leve ls, Chronic OR induced (1) the suppression of the diurnal ACTH/CORT rh ythm, with increased mean levels, especially for ACTH, (2) a degraded circadian locomotor activity rhythm manifested by a significant reduct ion in the spectral power of the 24h periodicity and a concomitant eme rgence of shorter (ultradian) periodicities, (3) an associated, but le ss pronounced alteration of the diurnal rhythm in body temperature; an d (4) a marked increase in baseline plasma levels of IL-1 beta and an increased reactivity in cytokine release following an E, coli endotoxi n (LPS) challenge. AOR induced (1) a similar obliteration of the circa dian ACTH/CORT rhythm, (2) the loss of close correlation between ACTH and CORT, (3) a generalized increase in baseline plasma IL-1 beta leve ls and (4) more extensive degradation of the circadian periodicity for both locomotor activity and, to a lesser extent, body temperature, re placed by dominant spectral powers for ultradian periodicities (3 to 1 0 h). In conclusion, both experimental paradigms - but AOR more than O R - caused a blockade of the circadian rhythmicity of major physiologi cal variables, the loss of normal correlations between ACTH and CORT, and inflammatory-immune hyperreactivity. These pathophysiological diso rders may all be parts of a complex chronic stress syndrome.