M. Svensson et al., EVIDENCE FOR ACTIVATION OF ASTROCYTES VIA REACTIVE MICROGLIAL CELLS FOLLOWING HYPOGLOSSAL NERVE TRANSECTION, Journal of neuroscience research, 35(4), 1993, pp. 373-381
Following peripheral nerve injury, resident microglial cells prolifera
te and astrocytes undergo hypertrophy, as evidenced, e.g., by an incre
ase in the levels of glial fibrillary acidic protein (GFAP). In a prev
ious study we have shown that infusion of cytosine arabinoside (ARA-C)
into the rat brain blocks the axotomy-induced proliferation of microg
lial cells. This experimental approach has been used in the present st
udy in order to explore the issue of whether the reactive microglial c
ells are mediators of the increased GFAP expression in the hypoglossal
nucleus of the rat following axotomy. Quantitative analysis of sectio
ns processed for immunocytochemistry or in situ hybridization demonstr
ated a marked increase in GFAP-like immunoreactivity and GFAP-mRNA, re
spectively, in the ipsilateral hypoglossal nucleus 4 and 7 days after
axotomy in control experiments. These increases failed to occur in axo
tomized animals treated with ARA-C. Therefore, our data are compatible
with the hypothesis that activation of astrocytes following axotomy a
s measured by increased expression of GFAP and its mRNA is induced sec
ondarily to the microglial response.