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.

Lesions in the medial posterior region of the BST impair sexual behavior in sexually experienced and inexperienced male rats.

Previous studies have showed that lesions in the bed nucleus of the stria terminalis of experienced male rats impair some parameters of sexual behavior. The aim of this study was to examine the contribution of the medial posterior region of the bed nucleus of the stria terminalis (BSTMP), a sexually dimorphic region of this nucleus that pertains to the vomeronasal system, to the modulation of sexual behavior of the male rat. Small electrolytic bilateral lesions in the BSTMP were made in male heterosexual experienced and inexperienced rats. Sham lesioned animals were also tested as a control of the effects of the general surgical procedures. Behavioral tests were then performed to obtain standard measures of masculine sexual behavior. Our results indicate that the sexually experienced male rats with lesioned BSTMPs showed increases in the number of mounts and the number of intromissions and, consequently, in ejaculation latency. In contrast, the sexually naive male rats showed increases in first mount and intromission latencies and in ejaculation latency, but the latter occurred due to increases in the interintromission intervals. This group also showed low correlations between olfactory investigation of the anogenital area of the female and initiation and maintenance of copulatory behavior. The results suggest that sexual experience obtained in the very artificial conditions of laboratory tests could supply some of the cues provided by the BSTMP in the process of sensorial integration, which we hypothesize modulates the initiation and pacing of copulation. However, sexual experience does not apparently supply any other kinds of cues provided or processed in the BSTMP that are involved in modulating the elicitation of intromissions and ejaculations.

MBR: a computer program to record and analyze parental behavior in rodents.

The Maternal Behavior Recorder (MBR) is a microcomputer program designed to record and analyze data from research on parental behavior of rats and other rodents. It is used to record the specific, characteristic patterns of maternal care in rodents: nest building, grooming, licking, crouching, and retrieval of pups. Moreover, it analyzes these events in terms of frequency and duration, allowing any events erroneously recorded to be corrected. The MBR can also simultaneously control observations made by one or two experimenters, and it calculates a set of reliability measures between them.

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. The inability of DHT in counteracting the effect of orchidectomy is addressed taking into account the inhibitory action of androgens.

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.

SBR: a computer program to record and analyse sexual behavior in rodents.

SBR (Sexual Behavior Recorder) is a program designed to record and analyse data from research on the sexual behavior of rats and other animals with similar patterns of sexual behavior. SBR allows the user to record the characteristic events of both the male and female's sexual behavior: mounts, intromissions, ejaculations and lordosis. It also allows the user to record two other types of events, and analyse them in terms of frequency and duration, using two user-defined keys. The program allows the correction of any event erroneously recorded. SBR can simultaneously control observations made by one or two observers, and on one or two experiment boxes. In the case that two observers record from the same experiment box, the program calculates a set of measures of reliability between the observers. At the end of each observation, SBR conducts a descriptive analysis of the recorded events, including the parameters normally used in scientific literature on the subject, and writes this analysis to disk files. As well as the default calculation parameters, it is possible to calculate any other, or to use the program as a record of general purpose events using the file which contains all the recorded events in sequential order and the exact time at which they were recorded. SBR was written using the compiler Turbobasic 1.1 from Borland International Inc. (1987).

Sexual dimorphism in the parastrial nucleus of the rat preoptic area.

This work investigates the possible existence of sex differences in the volume of the parastrial nucleus (PSN), a component of the preoptic area in the rat. The effects of postnatal (on day 1 after birth) male orchidectomy and female androgenization on this nucleus were studied. The volume of the PSN was greater in the control females than in the control males and postnatal treatments reversed this sexual dimorphism.

Early effects of gonadal steroids on the neuron number in the medial posterior region and the lateral division of the bed nucleus of the stria terminalis in the rat.

This work investigates the possible existence of sex differences in the number of neurons in the medial posterior region (BNSTMp) and the lateral division (BNSTL) of the bed nucleus of the stria terminalis in the rat. These two zones of the bed nucleus of the stria terminalis belong, respectively, to the vomeronasal system (VNS), and to the main olfactory system (MOS). In the BNSTMp, males showed a greater number of neurons than females. Early postnatal (Day 1 after birth) orchidectomy in males, and androgenization in females, eliminated and reversed these differences. In the BNSTL, sexual dimorphism was restricted to its anterior region (BNSTLa). Females showed there a greater number of neurons than males. Male orchidectomy on Day 1 after birth increased the number of neurons, while female androgenization produced the opposite effect. The results obtained in this study support the hypothesis that the VNS is sexodimorphic, and suggest that sex differences exist in MOS, and that these differences are controlled by gonadal steroids during the perinatal period.

The bed nucleus of the stria terminalis in the rat: regional sex differences controlled by gonadal steroids early after birth.

The effects of postnatal (on day 1 (D1) after birth) male orchidectomy and female androgenization on the bed nucleus of the stria terminalis (BNST) were studied. The volume of the medial posterior region of the BNST was greater in the control males than in the control females. Postnatal treatment reversed these differences. Sex differences were also found in the medial anterior region of the BNST where female rats always showed a greater volume than did the males. Female androgenization on D1 did not affect the volume of the BNST medial anterior region. However, D1 male orchidectomy did increase significantly the volume of this region. No sex differences were found in lateral, ventral or intermediate BNST divisions.