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early and late effects of perinatal hyper-gravity exposure on the developing CNs.    E. M. Sajdel-Sulkowska ^1,2, L. A. Baer ³, G-H Li ², G. M. Sulkowski ⁴, A. E Ronca ⁵, Charles E. Wade⁵. ¹Dept. of Psychiatry, Harvard Medical School and ²Brigham and Women’s Hospital, Boston MA; ³Lockheed Martin Engineering and Sciences, Moffett Field CA; ⁴ Harvard Medical School, Cambridge MA; ⁵Life Sciences Division, NASA/Ames Research Center, Moffett Field CA.

The results of previous experiments demonstrated that rats could successfully survive developmental exposure to 1.5G from gestational day 11 (G11) through postnatal day 21 (P21). However, their growth was compromised, with forebrain and cerebellum size decreased as compared with stationary control animals. The present study was designed to define the time-course of the hypergravity effect. Timed-pregnant Sprague-Dawley rats were exposed to continuous centrifugation at 1.5 G (HG; n=35) from G11 until one of six time points: P6, P9, P12, P18, P21, and P30. During the 41-day-long centrifugation, stationary controls (SC: n=34) were housed in the same room with HG rats. Neonatal body, forebrain, and cerebellum size were measured at each time point. All parameters were significantly affected (p>0.0001) in HG neonates at all times, but the degree and the time of maximal inhibition differed. HG neonates exhibited two time points at which maximal change was observed: maximal decrease in body mass was on P9 (26.77%) and P21 (23.79%); in brain size on P9 (13.47%) and P21 (10.42%); in cerebellar size on P6 (19.15%) and P21 (10.78%). These data support earlier speculations of Oyama and Platt (1967) that the general developmental effects of hypergravity are greatest just after birth and again at weaning. Furthermore, in the case of the cerebellum, the early effects of perinatal hypergravity exposure correspond to the critical period of granule cell proliferation, while the late effects correspond to cell differentiation. 

(Supported by NASA grant NCC2-1042.)