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At least 487 records · Page 27Linked to original sources
PubMed1992

Further evidence showing that the inhibitory action of serotonin on rat masculine sexual behavior is mediated after the stimulation of 5-HT1B receptors.

To explore whether the inhibitory actions of endogenous serotonin on rat male sexual behavior were mediated via the stimulation of the 5-hydroxytryptamine1A (5-HT1A) or 5-HT1B receptor subtypes, two series of studies were undertaken. In the first series, an attempt to block the inhibitory actions of threshold doses of the serotonin precursor 5-hydroxytryptophan (5-HTP, 50 mg/kg) by administering the beta-5-HT antagonist alprenolol (5.0 mg/kg) and the selective beta-blocker practolol (0.5 mg/kg) was made. Both antagonists effectively prevented, at least partially, the inhibitory actions of 5-HTP. In the second series, a possible synergistic effect of a subthreshold dose of 5-HTP (12.5 mg/kg) with low doses of the selective 5-HT1B agonist 1-(m-trifluoro-methylphenyl)piperazine (TFMPP,0.125 mg/kg) or the selective 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 0.0625 mg/kg) was investigated. A clear synergistic inhibitory effect of 5-HTP with TFMPP was observed. All data are interpreted based upon the hypothesis suggesting a physiological inhibitory role of the 5-HT1B receptor subtype on male rat sexual behavior.

5-Hydroxytryptophan↗
PubMed1995

Neurobiological correlates of masculine sexual behavior.

The experimental analysis of the neuroendocrine interactions regulating sexual behavior has traditionally relied on studying the effects of CNS lesions and pharmacological treatments with hormones or drugs purportedly acting through specific neurotransmitter systems. New methodological developments have allowed the assessment of several indices of neural function in experimental animals, particularly the rat, as they relate to behavioral changes. In the field of sexual behavior, ex vivo analyses have been used to measure markers of energy metabolism, such as 2-deoxyglucose uptake and Na,K-ATPase activity, the tissue content of neurotransmitters and metabolites, the levels of steroid receptors and neurosteroids, and immediate-early gene expression products in different areas of the CNS. In vivo studies have monitored brain electrical activity and temperature, as well as the extracellular levels of neurotransmitters and metabolites by cerebrospinal fluid sampling, push-pull perfusion and, especially, electrochemical recordings and microdialysis, in the course of mating and exposure to various relevant stimuli. The findings with the different methodologies are generally consistent and agree with those of previous surgical and pharmacological manipulations. They provide data on temporal relationships between neurobiological and behavioral events and suggest new interpretations for different aspects of the male copulatory pattern.

Animals↗
PubMed1992

Local perineal implants of anti-androgen block masculinization of the spinal nucleus of the bulbocavernosus.

Female rats were injected with testosterone propionate on the 1st and 3rd days of life. In addition, some females received 200 micrograms of the anti-androgen, hydroxyflutamide. Females receiving anti-androgen directly to the perineum, including the muscles bulbocavernosus and levator ani, had fewer surviving spinal nucleus of the bulbocavernosus (SNB) motoneurons than did females receiving the anti-androgen systemically. These results indicate that androgen acts upon the target muscles to spare developing SNB motoneurons from death.

Animals↗
PubMed1983

Tactile perception and the right hemisphere: a masculine superiority for imagery coding.

Recent research regarding hemispheric lateralization has suggested complex interactions among observed asymmetries, subject coding strategies, and sex differences in the utilization of and access to information codes. Prior to tactile perception of ambiguous figures, subjects were instructed to use either a verbal (left hemisphere) or imagery (right hemisphere) strategy. A non-instruction control group was included. Although a significant overall relationship between instructed strategy and tactile asymmetries was observed, this largely was due to males' privileged access to right-hemisphere imagery codes.

Attention↗
PubMed1991

Girls who use "masculine" problem-solving strategies on a spatial task: proposed genetic and environmental factors.

This study investigated strategy and performance differences between right-handed boys and girls on a mental rotation task. Based on predictions from Casey and Brabeck's (1990) theory of sex differences, the study was also designed to identify a target group of right-handed girls with the optimal combination of genetic and environmental factors (high math/science achievers with nonright-handed immediate relatives). They were predicted to show strategies and performance more similar to those of the boys than to those of both the low math/science achieving girls and the high math/science girls with all right-handed immediate relatives (predicted to have the nonoptimal genotype). Strategy preference was measured using selective interference, whereby subjects solved mental rotation items concurrently with either verbal or visual-spatial interference tasks. Group comparisons were made on the amount of decrement in mental rotation performance as a result of the two types of interference tasks. This provided a basis for comparing the groups on the use of visual-spatial or verbal strategies on the mental rotation task. The boys: (1) did not show a significant advantage over the girls on the mental rotation items, but (2) did depend more on visual-spatial strategies than the girls, and (3) depended less on verbal strategies than the girls. The target girls: (1) outperformed the low math/science achieving girls on the mental rotation items and did not show a significant advantage over the other high math/science group, (2) depended more on visual-spatial strategies than both the other two groups of girls, and (3) depended less on verbal strategies than the low math/science girls, while showing no significant difference compared to the nonoptimal high math/science girls. Examining within-group differences, the boys preferred visual-spatial strategies, while the girls in both the nontarget groups preferred verbal ones. However, for the target girls, no within-subject strategy differences were found. The present findings support the theory that, like the boys, the target girls depend more on visual-spatial strategies than do other girls. It is possible that the target girls use a combination of visual-spatial and verbal strategies when solving mental rotation tasks.

Adolescent↗
PubMed1995

Effects of fetal brain grafting on adult behavioral masculinization and defeminization in neonatally androgenized female rats.

Treatment of neonatal female rats with androgen results not only in decreased female sexual behavior but also in enhanced male sexual behavior examined in adulthood. The effects of grafting fetal preoptic area (POA) neurons into the POA, and fetal hypothalamic (HPT) neurons into the ventromedial hypothalamus (VMH), were tested in neonatally androgen-sterilized rats (ASR). The rats were injected subcutaneously with 80 micrograms testosterone propionate within the 24 hours after birth to see if sexual behavior could be normalized by fetal brain grafts. In repeated tests on ASR grafted with fetal HPT into the VMH, the lordotic response was seen to increase to the level seen in non-ASR controls, while the increase in mounting behavior in ASR was suppressed following grafting of fetal POA or cerebral cortex into the POA. These results suggest that there are dysfunctions of POA and VMH in ASR, and that the dysfunctions revealed by sexual behavior can be overcome by fetal POA or HPT grafting.

Androgens↗
PubMed2006

Masculinization of female golden rabbitfish Siganus guttatus using an aromatase inhibitor treatment during sex differentiation.

To elucidate the involvement of endogenous estrogen (estradiol-17beta; E2) and the decisive factor (somatic or germinal element) in the ovarian differentiation of tropical marine teleosts, the effect of the aromatase inhibitor (AI) fadrozole on gonadal sex differentiation in the golden rabbitfish Siganus guttatus (Bloch) was examined for different dosages and periods of treatment. Fadrozole interrupted ovarian cavity formation at a dose of 500 microg g(-1) diet, while there was little effect at 10 or 100 microg g(-1). The gonads from both the 30-day and 90-day administration (500 microg g(-1) diet) groups were significantly biased toward testes (P=0.002 and <0.0001, respectively), which suggests strongly that E2 is involved in early ovarian differentiation and that its suppression is an indispensable condition for testicular differentiation in S. guttatus. The results from the two different AI treatment periods imply that the initial feminization of somatic gonadal elements determines subsequent ovarian differentiation, including oogenesis: a conclusion supported by the considerable time lag between ovarian cavity formation and subsequent oogenesis during normal ovarian differentiation in S. guttatus.

Animals↗
PubMed2006

The human Y chromosome: a masculine chromosome.

Once considered to be a genetic wasteland of no scientific interest beyond sex determination, the human Y chromosome has made a significant comeback in the past few decades and is currently implicated in multiple diseases, including spermatogenic failure - absent or very low levels of sperm production. The Y chromosome contains over one hundred testis-specific transcripts, and several deletions have been described that remove some of these transcripts, thereby causing spermatogenic failure. Screening for such deletions in infertile men is now a standard part of clinical evaluation. Many other Y-chromosome structural variants, some of which affect gene copy number, have been reported recently, and future research will be necessary to address the phenotypic effect of these structural variants.

Animals↗
PubMed2004

Effects of chronic activity wheel running and imipramine on masculine copulatory behavior after olfactory bulbectomy.

We examined the effects of chronic activity wheel running and imipramine administration on appetitive behavior after olfactory bulbectomy (OBX). Male Long-Evans rats were randomly assigned to the following conditions using a 2 x 2 x 2 design: (1) bilateral OBX or sham surgery, (2) voluntary activity wheel running or sedentary home cage, and (3) daily imipramine or saline injections. After 21 days of treatment, animals underwent behavioral testing for copulatory activity and sucrose preference. Bulbectomized animals exhibited decrements in copulatory performance and reductions in sucrose intake compared to sham animals. Within the bulbectomized groups, imipramine-treated rats either did not copulate or had reduced ejaculation frequencies. However, activity wheel running attenuated the copulatory deficits induced by OBX. The findings encourage studies of physical activity and male sexual dysfunction among depressed men being treated by pharmacotherapy.

Animals↗
PubMed2006

Intersexuality and behavior in crayfish: the de-masculinization effects of androgenic gland ablation.

In crustaceans, male differentiation and primary and secondary characteristics are regulated by the androgenic gland (AG). In gonochoristic crustaceans, the AG is also linked to intersexuality. Whereas the co-occurrence of various male and female characteristics has been demonstrated in intersex crustaceans, little is known regarding sexually dimorphic behavior patterns in such individuals. In the present study, we used an intersex crayfish model to investigate--for the first time in crustaceans--the agonistic and mating behavior of intersex individuals, and to explore the effects of AG ablation on behavior, morphology and physiology. As was the case for their morphological and physiological reproductive traits, intersex individuals--despite being genotypically females--generally resembled males in terms of behavior: they engaged in fighting with males and copulated with receptive females. However, fighting durations of intersex animals were intermediate between those of males and females, and the durations of the copulations were remarkably short. Adult intersex individuals that had been AG ablated at the juvenile stage were unlikely to engage in fighting with males (similar behavior to females) and did not exhibit any mating behavior with receptive females. AG ablation resulted in feminine morphological and physiological shifts in the treated intersex individuals and enabled vitellogenin gene transcription and the onset of secondary vitellogenesis. It thus appears that an as-yet-unknown AG-secreted factor(s) regulating maleness also seems to regulate the organization of male behavior in crustaceans.

Agonistic Behavior↗
PubMed2006

Androgen receptors are required for full masculinization of the ventromedial hypothalamus (VMH) in rats.

The ventromedial hypothalamus (VMH) is one of several sexually dimorphic nuclei that regulate mating behavior, and is rich in steroid hormone receptors and aromatase activity. We looked at the contribution of the androgen receptor (AR) to the volume of the VMH in rats by measuring each of the four subdivisions of the VMH in 90 day old male, female, and XY male rats carrying a mutant AR allele (tfm), which renders animals largely unresponsive to androgens. Confirming published reports, total VMH volume was greater in wild-type males than in females (P<0.01). The mean total volume of the VMH in TFM males was intermediate, but not significantly different from either females or males (Ps>0.10). The sex difference in VMH volume was primarily accounted for by the ventrolateral subdivision (VMHvl), which in both females and TFM males was significantly smaller than in wild-type males (Ps<0.005). There was no significant sex difference in the volume of the other three subdivisions of the VMH. Neuronal somata were larger in males than females in VMHvl, central VMH (VMHc) and the dorsomedial VMH (VMHdm), with TFM males having feminine neuronal somata in the VMHdm and VMHc. These data suggest that AR plays a role during sexual differentiation of the VMH, imparting its greatest effect in the VMHvl. ARs may regulate aromatase expression or activity to affect estrogen receptor activation, or may act independently of estrogen receptors to influence VMH morphology.

Analysis of Variance↗