Journal of Neuroscience, Vol 9, 736-742, Copyright © 1989 by Society for Neuroscience
Androgen-specific critical periods for the organization of the major pelvic ganglion
JE Melvin and RW Hamill
Monroe Community Hospital, University of Rochester Medical Center, New York 14642.
Previous studies indicate that the major pelvic ganglion (PG) is dependent
on testosterone for normal development. Tyrosine hydroxylase (T-OH), DOPA
decarboxylase, and choline acetyltransferase (CAT) activities are
significantly reduced by postnatal castration on day 10- 11, while
testosterone replacement therapy reversed all developmental enzyme activity
deficits (Melvin and Hamill, 1987). In the present studies castration on
the day of birth combined with various testosterone-replacement paradigms
produced effects demonstrating that the PG is sensitive to testosterone
dosage and time of administration during early postnatal development.
Gonadal hormone replacement experiments show that the androgens
testosterone and dihydrotestosterone were effective in restoring T-OH and
CAT activity deficits produced by neonatal castration. Estrogen therapy
reversed the deficits in CAT activity, but was ineffective in reversing the
alterations in T-OH activity. Treatment of pregnant dams with the anti-
androgen flutamide altered the ontogeny of T-OH and CAT activities in pups
despite replacement therapy on the day of birth. Thus, androgen- critical
periods exist prenatally as well as postnatally. These studies suggest that
the organization of PG development is critically dependent on both the time
of exposure and dose of testosterone. Prenatal and postnatal critical
periods appear to exist. In addition, the lack of an effect of estradiol on
tyrosine hydroxylase activity suggests that androgens are specifically
responsible for organizing the noradrenergic development of the PG.