Castration increases and androgens decrease nitric oxide synthase activity in the brain: physiologic implications.

Sex differences in nitric oxide synthase (NOS) activity in different regions of the rat brain and effects of testosterone and dihydrotestosterone (DHT) treatment in orchidectomized animals were investigated. Regional but no sex differences in NOS activity were detected in gonadectomized animals. Orchidectomy significantly increased NOS activity in the hypothalamus, "amygdala," and cerebellum but not in the cortex.

Structural sexual dimorphisms in the anteroventral periventricular nucleus of the rat hypothalamus are sensitive to gonadal steroids perinatally, but develop peripubertally.

The volume of the anteroventral periventricular nucleus (AVPv) of the rat hypothalamus is larger in females than in males. A preliminary study from this laboratory found that this sexual dimorphism develops between days 30 and 91. The present study was designed to confirm and extend these findings and to determine the role of endogenous gonadal steroids in the development of the AVPv postnatally.

A revised critical period for the sexual differentiation of the sexually dimorphic nucleus of the preoptic area in the rat.

The volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) of the rat is several times larger in males than in females. Several studies have established the importance of gonadal steroids perinatally in the sexual differentiation of the SDN-POA as well as a critical period for the permanent influences of exogenous androgen on the volume of the nucleus. Recent preliminary evidence from this laboratory had suggested, however, that the critical period for the effects of the removal of endogenous gonadal steroids on SDN-POA volume may not match that for the administration of exogenous gonadal steroids.

Prenatal ethanol and the prepubertal sexually dimorphic nucleus of the preoptic area.

The volume of the sexually dimorphic nucleus of the preoptic area of the hypothalamus (SDN-POA) was determined in 14-31-day-old male and female rats whose mothers received a liquid diet containing 5% w/v ethanol from day 8 of gestation to parturition. Pair-fed dams received as a nutritional control an equal volume of an isocaloric liquid diet with maltose-dextrin in place of ethanol. Normal controls had laboratory rat chow and water available ad lib.

Onset of the hormone-sensitive perinatal period for sexual differentiation of the sexually dimorphic nucleus of the preoptic area in female rats.

The volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) of the rat brain is severalfold larger in males than in females. The volume of the SDN-POA can be influenced significantly by the hormonal milieu during the perinatal "critical period" of sexual differentiation of the brain. The purpose of the present study was to determine the onset of this period of sexual differentiation of the SDN-POA.