Jy. Tseng et al., ESTROGEN REGULATES GALANIN BUT NOT TYROSINE-HYDROXYLASE GENE-EXPRESSION IN THE RAT LOCUS-CERULEUS, Molecular brain research, 50(1-2), 1997, pp. 100-106
The neuropeptide galanin (GAL) is coexpressed by the majority of norad
renergic neurons in the rat locus ceruleus (LC) and may function as an
inhibitory modulator of noradrenergic transmission. Because estrogen
has been shown to induce GAL expression in other brain regions and mod
ulate noradrenergic transmission, we used in situ hybridization histoc
hemistry to assess the effects of chronic estrogen treatment on GAL an
d tyrosine hydroxylase (TW) gene expression in the LC of ovariectomize
d female rats. We found that GAL mRNA levels were significantly elevat
ed in rats implanted with a Silastic capsule containing estradiol comp
ared to sham-implanted controls. Both the average optical density (P l
ess than or equal to 0.05) and the labelling area (P less than or equa
l to 0.007) differed significantly between the groups. In contrast, TH
gene expression measured in alternate brain sections did not differ b
etween the groups. If GAL functions as an inhibitory modulator of nora
drenergic transmission as postulated, these findings suggest that chro
nic estrogen treatment could reduce the noradrenergic tone of the brai
n in the absence of significant alterations in TH expression by enhanc
ing the level of cosecreted GAL. (C) 1997 Elsevier Science B.V.