Effects of Adrenal Medulla Transplantation into the Third Ventricle on the Onset of Puberty in Female Rhesus Monkeys

Abstract

To test the hypothesis that prepubertal exposure of LHRH neurons to a source of catecholamines and neuropeptides accelerates the onset of puberty, we examined the effects of autologous adrenal transplantation into the base of the third ventricle of the brain in juvenile female rhesus monkeys at 11–13 months of age. The adrenal medulla, which contains catecholamines and neuropeptide Y (NPY), was cut into small pieces and mixed with gelfoam in artificial CSF and injected into the third ventricle, adjacent to LHRH neurons and their neuroterminals. Sham control monkeys received artificial CSF with gelfoam alone. Animals were monitored for signs of pubertal development. While menarche was not altered by adrenal transplantation, the timing of first and second ovulations occurred significantly (P<0.05) earlier in adrenal-transplanted monkeys. Histological examination indicated that the grafts survived in all transplanted monkeys. The presence of catecholamines and NPY in graft tissue was confirmed by tyrosine-hydroxylase-positive, dopamine β-hydroxylase-positive, and NPY-positive cells. Endogenous LHRH fibers were observed innervating the graft tissue. We conclude that: (1) adrenal medulla transplantation into the third ventricle accelerates the age of first ovulation; (2) this is likely due to neuroactive substances (e.g., catecholamines and NPY) from the graft tissue; and (3) grafted adrenal medulla tissue can survive for at least 30–40 months. However, the age of menarche was not accelerated by this grafting, suggesting that an additional mechanism (e.g., removal of tonic inhibition) may be necessary for the onset of puberty.