Lack of interaction between prenatal stress and prenatal letrozole to induce same-sex preference in male rats

Multiparity favors same-sex partner preference in male rats

Same-sex partner preference is present in many mammals, including rodents. Several possible causal factors have been proposed for the establishment of this preference. The Fraternal Birth Order effect refers to the observation that older brothers increase the probability of homosexuality in men, but no experiment has analyzed this possibility. In this study, partner preference (tested in a three compartments box) and female and male sexual behavior (studied in a cylindrical arena) were evaluated in young male rats (3 months) born to multiparous mothers that had 4-6 previous gestations and around 12 months of age. Control groups were young male rats born to primiparous young (4 months) or aged (12 months) mothers. In the partner preference test, the males born to multiparous dams spent less time interacting with the receptive female and more time interacting with the sexually active male, and a 39% exhibited same-sex partner preference. This high percentage seems related to multiparity of their mothers and not to maternal age, because the males born to primiparous aged females (12 months) showed a similar low proportion of same-sex partner preference than the males born to young (4 months) primiparous females (4%). In the sexual behavior tests, no male born of a multiparous dam and with same-sex preference ejaculated and 54% displayed proceptivity and lordosis. Present results suggest that the fraternal birth order effect may occur also in rats.

Induced Stress and Tactile Stimulation Applied to Primiparous does and their Consequences on Maternal Behavior, Human-Animal Relationships, and Future Offspring's Sexual Disorders

The aim of this study was to investigate whether tactile stimulation in rabbits during the gestation phase improve the maternal behavior and human-animal relationships as well as the effects on reproductive behavior of male kits when reached maturity compared to induced stress. A total of 33 primiparous New Zealand does were selected after pregnancy confirmation and allocated in a randomized complete block design. The treatments applied were as follows: (C) animals not stimulated during the experimental period; (TS) animals that received tactile stimulation; and (SS) does which were immobilized. The nest building behavior as well as the weight, sexual behavior, mortality, and semen analysis of the offspring was recorded. In addition, the novel object, flight distance, social isolation, and human-approach tests were conducted. Under the conditions of the present trial, TS animals showed more trust in the unfamiliar observer when compared to the other two treatments. The treatments applied to the females (TS and SS) were sufficient to confirm that the control group presented better values for the number of stillbirths and the proportion of deaths in the first week. Finally, the handling of does reduce the males' ejaculation and sperm presence but not inhibited sexual behavior or impaired semen quality. It is possible to conclude that TS did not impair does welfare or maternal behavior and it improved the human-animal relationship, however there was a negative impact on the litter. More studies that directly assess impact on the future reproductive capacity of the offspring are necessary.

Retracted: Sexual orientation, neuropsychiatric disorders and the neurotransmitters involved

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor in Chief of Neuroscience and Biobehavioral Reviews after concerns were raised with respect to the phrasing of comparisons drawn between humans and animal models. These comparisons were deemed unsupportable, and thus in the best interests of publication standards the Editor has concluded it is necessary to retract the paper. The authors disagree with the reason for the retraction.