The relationship between temperament and sexual orientation.

BACKGROUND: The relationship between temperament and sexual orientation has been poorly characterized. We have used the Affective and Emotional Composite Temperament (AFECT) model to evaluate this association in a large population sample. METHODS: Data from 16,571 subjects between 21 and 45 years old (mean age=29.1±6.3 yrs, 69.4% females) was collected anonymously through Internet in Brazil. RESULTS: Regarding affective temperaments, male cyclothymics and dysphorics had the lowest percentage of people with heterosexual orientation and the highest percentages of people with bisexual and homosexual orientations. The opposite profile was observed in hyperthymic and euthymic types. Among females, the volatile, cyclothymic, apathetic, disinhibited and euphoric types were less often observed in people with "pure" heterosexual orientation and more often in people with bisexual orientation. In men only, homosexuality was more common among the depressive, cyclothymic and dyphorics temperaments. Emotional trait analysis showed that heterosexual subjects differed statistically from all other groups by having higher scores of coping and stability and lower scores of sensitivity and desire. Overall, the effect sizes were small to moderate, with the largest differences between "pure" heterosexuals and people with bisexual orientation, particularly in women. Subjects with heterosexual orientation who have had homosexual experience and those with homosexual orientation presented intermediate scores. LIMITATIONS: Cross-sectional design, lack of potentially important covariates (e.g., maltreatment) and data collected by Internet only. CONCLUSION: Externalized and unstable traits were associated mainly with bisexuality. The group of heterosexuals with homosexual fantasies or experiences offers a new approach for the study of sexual orientation.

Sustained behavioral effects of lithium exposure during early development in zebrafish: involvement of the Wnt-ß-catenin signaling pathway.

Lithium has been the paradigmatic treatment for bipolar disorder since 1950s, offering prophylactic and acute efficacy against maniac and depressive episodes. Its use during early pregnancy and the perinatal period remains controversial due to reports of negative consequences on the newborn including teratogenic and neurobehavioral effects generally referred as Floppy baby syndrome. The mechanisms underlying lithium therapeutic action are still elusive but exacerbation of Wnt signaling pathway due to GSK-3 inhibition is believed to represent its main effect. In this study we evaluated the impact of lithium exposure during zebrafish embryonic and early development including behavioral and molecular characterization of Wnt-ß-catenin pathway components. Wild-type zebrafish embryos were individually treated for 72 hpf with LiCl at 0.05, 0.5 and 5mM. No significant teratogenic and embryotoxic effects were observed. At the end of treatment period western blot analysis of selected Wnt-ß-catenin system components showed increased ß-catenin and decreased N-cadherin protein levels, without significant changes in Wnt3a, supporting GSK-3 inhibition as lithium's main target. At 10 dpf 0.5 and 5mM lithium-treated larvae showed a dose-dependent decrease in locomotion among other exploratory parameters, resembling lithium-induced Floppy baby syndrome neurobehavioral symptoms in humans. At this later period previously altered proteins returned to control levels in treated groups, suggesting that the neurobehavioral effects are a lasting consequence of lithium exposure during early development. RT-qPCR analysis of ß-catenin and N-cadherin gene expression showed no effects of lithium at 3 or 10 dpf, suggesting that protein fluctuations were likely due to post-transcriptional events. Other Wnt target genes were evaluated and only discrete alterations were observed. These results suggest that zebrafish may be a valuable model for investigation of early effects of lithium that may be mediated by effects on the Wnt signaling pathway.

One for all and all for one: the importance of shoaling on behavioral and stress responses in zebrafish.

Zebrafish has been increasingly used in behavioral studies, but data can present high variability. Most studies have been performed using isolated zebrafish, despite their interactive nature and shoaling behavior. We compared adult zebrafish behavior and cortisol levels after exposure to novelty as well as sensitivity to Pentylenetetrazole (PTZ)-induced seizures in animals tested individually or in groups of three (triplets). In the exploratory behavior task, data from single fish and triplets were not significantly different, but single fish data were more disperse in latency, to enter and time spent in the tank upper part, and crossings. In the light-dark task, time in the light zone and crossings were not different between groups, but latency to enter the dark zone and data variability were. We also observed that the latency to reach stage III seizures induced by PTZ was higher in triplets, but data dispersion was not different from single fish. Finally, cortisol levels of fish individually exposed to a novel environment were higher and more variable than triplets, while both groups had higher levels than unmanipulated animals. Thus, when tested individually, zebrafish are more stressed and present more variable behavior due to disruption of their natural shoal strategies. These features can be beneficial or detrimental depending on study aims and should be considered when designing, analyzing, and interpreting zebrafish behavioral data.

A one-trial inhibitory avoidance task to zebrafish: rapid acquisition of an NMDA-dependent long-term memory.

The behavioral tasks aiming to evaluate learning and memory mechanisms currently available to zebrafish (Danio rerio) involve long training sessions frequently along multiple days and are based on shuttle box or active-avoidance protocols, preventing a detailed analysis of cellular and molecular time-dependent processes involved in memory acquisition and consolidation. In order to explore zebrafish's potential contribution to the characterization of the molecular machinery underlying learning and memory rapidly acquired and reliable paradigms are necessary. In this study we present a rapid and effective learning protocol in a single-trial inhibitory avoidance in zebrafish. In a simple apparatus, adult animals learned to refrain from swimming from a white into a dark compartment in order to avoid an electric shock during a single-trial training session that lasted less than 2 min. The resulting memory is robust, long-lasting and sensitive to NMDA-receptor antagonist MK-801 given in the tank water immediately after training. Experiments aiming to further characterize the events underlying memory formation, retrieval or extinction or those looking for cognitive profiling of mutants, neurotoxicological studies and disease models may benefit from this task, and together with complementary strategies available for zebrafish may significantly improve our current knowledge on learning and memory mechanisms.