Tyrosine hydroxylase and norepinephrine transporter in sympathetic ganglia of female rats vary with reproductive state

In females, sympathetic activity varies with changes in reproductive status, but whether expression of proteins critical to the function of sympathetic neurons is also altered is unknown. Therefore, the present study tested the hypothesis that, in rat adrenal gland and superior cervical ganglia, the expression of tyrosine hydroxylase (TH) and the norepinephrine transporter (NET), measured using Western analysis, are changed during pregnancy and the estrous cycle. Compared to diestrus, pregnancy increased TH levels in both superior cervical ganglia and adrenal gland. Pregnancy was also associated with decreased NET levels in the superior cervical ganglia, but increased levels in the adrenal gland. Relative to diestrus, the pattern of changes of TH and the NET in rats during proestrus was generally similar to changes observed during pregnancy. To assess whether gonadal hormones were involved, ovariectomized rats were also studied and changes in serum estrogen and progesterone were assayed in a subset of animals in all groups. Variations in TH and the NET among all groups did not correlate with changes in either estrogen or progesterone, suggesting that the steroids were not exclusively responsible. In conclusion, reproductive status alters the expression of TH and the NET in adrenal gland and superior cervical ganglia of female rats, which could significantly influence the function of the sympathetic nervous system. However, the mechanism for these changes does not depend solely on changes in estrogen or progesterone.