3.5 Differential responses of PrL and IL to astrocyte
alterations induced by ICV-STZ.
Then, we evaluated the expression and function of astrocytes in the PrL
and IL separately. GFAP was considered as the astrocyte marker. In the
PrL, the main effects of ICV-STZ were observed in the intersection
number (12 μm: F(1,20)=5.075; 15 μm:
F(1,20)=7.447), levels of GLAST
(F(1,20)=8.530), GFAP (F(1,20)=8.883)
and KA (F(1,20)=20.43); the main effects of 1-MT
treatment were observed in the intersection number (3 μm:
F(1,20)=5.057; 9 μm: F(1,20)=4.648; 12
μm: F(1,20)=7.488; 15 μm: F(1,20)=18.27;
18 μm: F(1,20)=24.75; 21 μm:
F(1,20)=17.39; 24 μm: F(1,20)=7.569),
levels of GLT-1 (F(1,20)=9.437), GLAST
(F(1,20)=5.884), GFAP (F(1,20)=10.77)
and KA (F(1,20)=38.04). A significant interaction
between ICV-STZ and 1-MT treatment was observed in the GFAP-positive
cell number (F(1,20)=21.19), intersection number (12 μm:
F(1,20)=5.959; 15 μm: F(1,20)=8.523; 18
μm: F(1,20)=5.719; 21 μm:
F(1,20)=7.213), levels of GLAST
(F(1,20)=14.21) and KA (F(1,20)=17.85).
ICV-STZ significantly reduced the number of GFAP-positive cells in the
PrL, which was reversed by intra-PrL injection of 1-MT (Figure 7A, B).
Sholl analysis showed an attenuated number of intersections, suggesting
the atrophy of astrocytes. Specifically, the ICV-STZ rats significantly
decreased at steps 9 and 12 compared with the vehicle rats, and a
significant increase in the number of intersections was found in the
intra-PrL injection of 1-MT rats at steps 9 to 24 compared with ICV-STZ
rats (Figure 7C, D). Consistent with above results, western blot
analysis (Figure 7E) also revealed that ICV-STZ markedly decreased the
expression of GFAP (Figure 7H) in the PrL, accompanied by dysfunctional
changes including the reduction of GLT-1 (Figure 7F) and GLAST (Figure
7G). All these defects were restored by intra-PrL injection of 1-MT
(Figure 7E-H). Levels of KA decreased with astrocyte deficits in the
PrL, and this decrease was reversed by intra-PrL injection of 1-MT
(Figure 7I). In the IL, the main effects of ICV-STZ were observed in the
intersection number (12 μm: F(1,20)=5.809; 21 μm:
F(1,20)=4.424) and levels of KA
(F(1,20)=10.61); the main effects of 1-MT treatment were
observed in the levels of GFAP (F(1,20)=17.08). ICV-STZ
and intra-IL injection of 1-MT had no effect on the number of astrocytes
per unit area (Figure 8A, B). In addition, there was no significant
distinction in the number of intersections for all groups (Figure 8C,
D). Western blot analysis (Figure 8E-H) did not reveal a significant
difference in the expression of GLT-1 (Figure 8F), GLAST (Figure 8G) and
GFAP (Figure 8H) in the IL across the groups. Intriguingly, the levels
of KA also decreased in the IL, and did not reverse by intra-IL
injection of 1-MT (Figure 8I).