Invited Symposium: Behaviour-Induced Neural Events after Brain Injury
An ANOVA revealed a significant effect of treatment on the Sv of GFAP immunoreactive processes in the SON (F 2,8 = 17.8, P < 0.003). As shown in Figure 5 subsequent comparisons showed that 7 days of dehydration resulted in an significant decrease in Sv of GFAP immunoreactive processes in comparison to control and dehydrated/rehydrated rats (P < 0.05).
Fig.5: The surface density of GFAP-IR processes in the SON. C = control; D = dehydrated; D/R = dehydrated/rehydrated. Differences among the groups were tested by Student-Neuman-Keuls test. * P < 0.05
. Overall, there was a 15 % and 10 % reduction of Sv in the dehydrated group relative to the control and rehydrated groups respectively. As shown in Figure 6 the GFAP staining of the globus pallidus and lateral hypothalamus was not significantly affected by the treatment conditions (Fig. 6, F's 2,8 = 0.349; 0.423)
Fig.6: The surface density of GFAP-IR processes in the globus pallidus and lateral hypothalamic area measured in the same sections from which the the SON Sv data was collected. C = control; D = dehydrated; D/R = dehydrated/rehydrated. There were no signifincant differences among the groups.
A change in the number of glia (astrocytes) in the VGL could contribute to the decrease in Sv. However, we found no significant effect of dehydration on the number of astrocytes in the VGL (Table 1).
Table 1 Astrocyte Numerical Density (Nv) in the SON-VGL C D D/R Nv (cells per mm3) 16 ± 0.25 17 ± 0.25 16 ± 0.22 (x 104) C = control; D= dehydrated; D/R = dehydrated/rehydratedNevertheless the ratio of Sv for GFAP-positive processes to astrocytes in the VGL [Sv(astrocytes)/Nv(astrocytes)] was significantly altered by dehydration (F 2,8 = 11.81, P < 0.001). As shown in Figure 7 post hoc comparisons indicated that the [Sv(astrocytes)/Nv(astrocytes)] in the dehydrated group was significantly decreased in comparison to the others groups (P < 0.05)
Fig.7: The ratio of surface density of GFAP-IR processes in the SON to Nv astrocytes in the SON-VGL. C = control; D = dehydrated; D/R = dehydrated/rehydrated. Differences among the groups were tested by Student-Neuman-Keuls test. * P < 0.05
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|Hawrylak, N; Sedlmeyer, T; Boone, D; Salm, AK; (1998). Dehydration and Rehydration Reversibly Alter the Surface Density of Glial Fibrillary Acidic Protein Immunoreactivity (GFAP-IR) of Astrocytes in the Rat Supraoptic Nucleus. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/schallert/hawrylak0850/index.html|
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