The development of sex differences in the locus coeruleus of the rat.

Development of sex differences in the locus coeruleus (LC) is investigated. The LC is a sexually dimorphic structure in which the female manifests a larger volume and greater number of neurons than do males. Male and female Wistar rats were sacrificed on prenatal days (E) 16 and 20 and postnatally (P) on days 1, 3, 7, 15, 35, 45, 60, and 90.

The development of brain sex differences: a multisignaling process.

In order to account for the development of sex differences in the brain, we took, as an integrative model, the vomeronasal pathway, which is involved in the control of reproductive physiology and behavior. The fact that brain sex differences take place in complex neural networks will help to develop a motivational theory of sex differences in reproductive behaviors. We also address the classic genomic actions in which three agents (the hormone, the intracellular receptor, and the transcription function) play an important role in brain differentiation, but we also point out refinements that such a theory requires if we want to account of the existence of two morphological patterns of sex differences in the brain, one in which males show greater morphological measures (neuron numbers and/or volume) than females and the opposite.

Estradiol masculinizes the number of accessory olfactory bulb mitral cells in the rat.

Orchidectomized males injected with a single dose of estradiol benzoate on the day of birth (D1) showed mitral cell numbers in the accessory olfactory bulb similar to those of control males. However, orchidectomized males that received no additional estradiol benzoate treatment and those orchidectomized and given a single dose of dihydrotestosterone on D1 showed decreases in the number of accessory olfactory bulb mitral cells compared with control males. These results support the notion that the presence of estradiol immediately after birth induces the masculinization of mitral cells number in the accessory olfactory bulb.

Early postnatal diazepam exposure facilitates maternal behavior in virgin female rats.

Virgin female rats do not display maternal behavior if they are not exposed to the pups during several days. This exposure is called induction. In this work we have studied the effects of early postnatal (PO-P16) diazepam (DZ) administration (1 and 2.

Perinatal administration of diazepam alters sexual dimorphism in the rat accessory olfactory bulb.

The present study examines the effects of pre and/or early postnatal administration of diazepam on the mitral cell and on the light and dark granule cell populations in the sexually dimorphic accessory olfactory bulb of the rat. Quantitative differences related to sex were observed in the numbers of the three types of neurons, with vehicle males showing greater numbers of cells than vehicle females. The number of mitral cells in males decreased to the levels shown by female rats following prenatal and pre-postnatal diazepam treatments, whereas the DZ treatments did not affect the females.

Effects of estradiol on the development of sexual dimorphism in the bed nucleus of the accessory olfactory tract in the rat.

Orchidectomized males injected with a single dose of estradiol benzoate (EB) on the day of birth (D1) showed a volume and neuron number in the nucleus of the accessory olfactory tract (BAOT) similar to that of control males. However, orchidectomized males and those orchidectomized and given a single dose of DHT on D1 showed a decrease in BAOT volume and neuron number with respect to control males. These results support the notion that estradiol induces the morphological masculinization of this structure.

Effects of perinatal diazepam exposure on the sexually dimorphic rat locus coeruleus.

Diazepam (DZ) administration over prenatal, postnatal, and pre plus postnatal periods altered the normal expression of the morphological sex differences of the LC. Males were affected only by the prenatal exposure and the effect of this exposure produced an increase in the volume and neuron number of male's LC. By contrast, females were affected by both pre and postnatal treatments and the effect of this exposure resulted in a decrease in the volume and neuron number of female's LC.

Altered stressor-induced changes in GABAA receptor function in the cerebral cortex of adult rats exposed in utero to diazepam.

Prenatal administration of the anxiolytic drug diazepam (DZP), 2.5 mg/kg) to the pregnant rat over gestational days 14-20 altered function and stressor-induced responsiveness of the GABAA receptor in the cerebral cortex of exposed animals as adults. In Experiment 1, the impact of 15 min of restraint on chloride-facilitated benzodiazepine binding was evaluated in male and female rats at 70-90 days of age.

Postnatal administration of dihydrotestosterone to the male rat abolishes sexual dimorphism in the accessory olfactory bulb: a volumetric study.

The regulatory action of the non-aromatizable androgen dihydrotestosterone (DHT) on sexual differentiation of the volume of the rat accessory olfactory bulb (AOB) was studied. Postnatal treatment with DHT (180 micrograms/day) carried out daily between days 6 and 20 produced a drastic reduction in overall AOB size and that of its constituent neural layers in genetic males with respect to intact and control males. The volumetric measures found in DHT-treated males did not differ from those shown by the intact females.

Effects of early postnatal sex steroids on acquisition and extinction of a continuously reinforced lever-pressing response.

The effects of early postnatal dihydrotestosterone (DHT) and estradiol on the sexually dimorphic continuously reinforced lever-pressing response were investigated. 90-day-old male rats postnatally treated (during the first eight days of postnatal life) with cyproterone acetate (CA), tamoxifen (TX) or vehicle, and 90-day-old females treated with estradiol benzoate (EB), DHT or vehicle in the same postnatal period, were studied during the acquisition and extinction of the continuously reinforced lever-pressing response using a free-operant procedure. During acquisition, the control males made more responses per minute than the control females, and also reached the extinction criterion significantly sooner than the females.

Early postnatal diazepam exposure alters sex differences in the rat brain.

The volume and neuron number of the sexually dimorphic accessory olfactory bulb and locus coeruleus are altered by early postnatal exposure (from the day of birth to postnatal day 16) to diazepam. After diazepam treatment, both volume and neuron number were decreased in the male accessory olfactory bulb and in the female locus coeruleus. These results indicate that early postnatal diazepam administration can bear gender-dependent teratogenic effects upon sexually dimorphic nuclei and suggest that endogenous benzodiazepines may be involved in the sexual differentiation of the brain.

Effects of perinatal diazepam administration on two sexually dimorphic nonreproductive behaviors.

The effects of prenatal and/or early postnatal diazepam (DZ) administration on open field activity and continuously reinforced lever-pressing response were studied. Rat pups of both sexes were prenatally (during the last week of pregnancy) and/or postnatally (from the day of birth to day 16) daily exposed to a 2.5 mg/kg dose of DZ.