Hormonal regulation of sympathetic neuron development. The effects of neonatal castration

The effects of neonatal castration on neuronal ontogeny were examined in peripheral sympathetic ganglia in male Sprague-Dawley rats. Tyrosine hydroxylase (T-OH) activity, the rate-limiting enzyme in catecholamine biosynthesis and a marker of noradrenergic maturation, was examined in the hypogastric (HG) and superior cervical ganglion (SCG). Initial studies characterized the normal development of T-OH activity in HG ganglia. Neonatal castration at 10-11 days of age prevented the normal ontogeny of HG T-OH activity: T-OH activity failed to develop normally and was 17% of sham-operated littermate controls when examined at 8 weeks of age, and less than 5% when studied 10 weeks after surgery. In contrast to the effects in HG, there was no change in enzyme activity in the SCG. Replacement therapy with testosterone decanoate completely reversed the developmental alteration in enzyme activity. These observations suggest that hormonal factors modulate noradrenergic ontogeny in peripheral sympathetic ganglia but these effects appear restricted to ganglia whose targets include hormonally dependent sex organs.