Immunocytochemical analysis of sex differences in calcitonin gene-related peptide in the rat dorsal root ganglion, with special reference to estrogen and its receptor
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Abstract
Previous studies have shown that the calcitonin gene-related peptide (CGRP) immunoreactivity
in the central nervous system (CNS) of adult rats is sexually dimorphic and regulated
by sex steroid. In the present study, we used immunocytochemistry to investigate the
sex difference in CGRP-immunoreactive (IR) neurons in rat dorsal root ganglia (DRG).
The numbers of CGRP-IR neurons at the cervical, lumbar and sacral levels in the female
rats were significantly lower than those of the male rats. We also found that the
number of CGRP-IR neurons at the lumbar level was increased in ovariectomized (OVX)
rats, but was decreased in estradiol (E2)-treated rats (OVX+E2). A large number of
estrogen receptor (ER)-IR neurons at the lumbar level were found in the female rats,
and its number was greater than that in the male rats. We also investigated the change
in the number of ER-IR neurons of OVX rats after estrogen treatment. The number of
ER-IR neurons in the OVX+E2 rats was consistent with that of the intact female rats,
but was significantly increased in the OVX rats. As shown by a double-labeling immunocytochemical
method, over 80% of the CGRP-IR neurons at the lumbar level showed ER immunoreactivity
in the female, OVX and OVX+E2 rats, compared to only about 46% in the male rats. These
results indicate that there is a gender difference in CGRP expression in the rat DRG,
and that this CGRP expression might be downregulated by estrogen (at least in part)
through its receptor.
Copyright 1998 Elsevier Science B.V.