Biochemical and Morphological Effects of Testosterone Treatment on Developing Sympathetic Neurons

Neonatal rats were treated with testosterone propionate (TP) or isoproterenol (ISO) to determine whether (1) increases in salivary gland mass are associated with alteration of developing sympathetic neurons and (2) whether effects on neuron growth are secondary to altered target mass itself or to increases in salivary growth factors. TP treatment is known to result in salivary tubule hypertrophy and elevated nerve growth factor (NGF) content whereas IS0 treatment results in acinar hypertrophy and no known alteration in NGF. TP treatment increased submaxillary gland weight as well as tyrosine hydroxylase (T‐OH) activity, adrenergic neuron numbers and total protein in the innervating superior cervical ganglion (SCG). Unilateral sialectomy prevented the increase in T‐OH activity in the SCG, suggesting that the salivary glands were necessary for this effect. T‐OH activity and total protein were elevated in the distant sixth lumbar sympathetic ganglion after TP treatment, suggesting that sympathetic development as a whole was affected and that humoral factors may be involved. Salivary gland weight was also elevated following ISO administration, but T‐OH activity in the SCG was not affected. These observations suggest that TP treatment increases T‐OH activity and sympathetic neuron numbers by alteration of specific salivary humoral growth factor(s).