The effect of taget organ removal on the development of sympathetic neurons

The role of target organs in the maturation of adrenergic neurons was studied in the neonatal rat. The superior cervical ganglion (SCG) and its end organs, the salivary glands and iris were employed as a model system. Unilateral sialectomy and iridectomy in 3-day-old animals prevented the normal development of ganglion tyrosine hydroxylase (T-OH) and DOPA decarboxylase activities. These enzymes are highly localized to adrenergic neurons in the SCG, and were used to monitor maturation of these cells. Enzyme activity remained depressed for at least two months, the longest time tested. In contrast, total ganglion protein, a measure of ganglion growth as a whole, initially developed normally. Six weeks after surgery, however, protein content was significantly lower in ganglia deprived of the normal field of innervation. Failure of normal enzyme maturation was apparently dependent on removal of ipsilateral end organs only, since bilateral sialectomy exerted no greater effect than unilateral sialectomy. In adults, unilateral sialectomy and iridectomy did not significantly alter ganglion T-OH activity or protein in rats followed up to one month after surgery.