Increased number of sympathetic neurons with unchanged target organ innervation after postnatal polyamine treatment

Abstract Treatment of newborn rats with polyamines from day 2 to day 9 after birth prevented the normal reduction in the number of sympathetic neurons in the superior cervical ganglion. About 40% more neurons prevailed in the ganglion after the polyamine treatment. This increase was paralleled by a comparable developmental increase in tyrosine hydroxylase activity and a small (17%) increase in choline acetyltransferase activity in the ganglion. However, in the iris, a target organ innervated by the sympathetic neurons, tyrosine hydroxylase activity and [ 3 H]norepinephrine uptake remained unchanged. The results indicate that the polyamine-induced increase in the number of parent neurons is not accompanied by a change in the number of functional nerve terminals in the target organ.