Water deprivation and rat adrenal mRNAs for tyrosine hydroxylase and the norepinephrine transporter

Experiments were performed in rats to test the hypothesis that adrenal mRNA levels of tyrosine hydroxylase (TH) and the norepinephrine transporter (NET) would be modified by water deprivation via activation of the sympathetic nervous system. TH and NET mRNA levels were measured using the ribonuclease protection assay. Adrenal TH mRNA was higher (P < 0.001) in water-deprived (921 ± 39 fg/μg total RNA) compared with the water-replete rats (657 ± 45 fg/μg total RNA). In contrast, water deprivation decreased (P < 0.01) adrenal NET mRNA levels (275 ± 66 vs. 433 ± 63 fg/μg total RNA). The dehydration-induced increase in TH mRNA was prevented by prior splanchnicectomy, but the decrease in NET mRNA was produced even in the absence of adrenal nerves. Water deprivation also increased (P < 0.05) plasma adrenocorticotropic hormone (84 ± 16 vs. 42 ± 14 pg/ml) and corticosterone (358 ± 87 vs. 44 ± 15 ng/ml) levels. Interestingly, the corticosterone response was reduced (P < 0.05) by unilateral adrenal denervation. These results suggest that water deprivation increases both adrenal medullary and adrenocortical activity at least in part by stimulation of sympathetic nerve activity.