INNERVATION-INDEPENDENT CHANGES IN THE MESSENGER-RNAS ENCODING TYROSINE-HYDROXYLASE AND THE NOREPINEPHRINE TRANSPORTER IN RAT ADRENAL-MEDULLA AFTER HIGH-DOSE RESERPINE

To determine whether a trans-synaptic mechanism triggered the effects of reserpine on adrenomedullary mRNAs encoding the norepinephrine tran sporter and tyrosine hydroxylase, we administered 10 mg/kg reserpine t o rats after unilateral splanchnicotomy, and examined their adrenal me dullas using quantitative in situ hybridization. Splanchnicotomy did n ot alter the decrease in norepinephrine transporter mRNA that follows reserpine administration, but diminished the reserpine-induced increas e in tyrosine hydroxylase mRNA by almost 80%. Despite the latter effec t, reserpine still induced a significant increase in tyrosine hydroxyl ase mRNA in denervated adrenal medullas, compared to vehicle-treated a drenal medullas. These results show that a trans-synaptic mechanism do es not trigger the decrease in adrenomedullary norepinephrine transpor ter mRNA following reserpine. In addition, an innervation-independent mechanism mediates a portion of the reserpine-induced increase in adre nomedullary tyrosine hydroxylase mRNA.