Modelling sexual violence in male rats: The sexual aggression test (SxAT)

Sexual assault and rape are crimes that impact victims worldwide. Although the psychosocial and eco-evolutionary factors associated with this antisocial behavior have repeatedly been studied, the underlying neurobiological mechanisms are still unknown mainly due to the lack of an appropriate animal model of sexual aggression (SxA). Here, we established a novel paradigm to provoke and subsequently assess SxA in adult male Wistar rats: the sexual aggression test (SxAT). Briefly, male Wistar rats are sexually aroused by a receptive female, which is exchanged by a non-receptive female immediately after the first intromission. This protocol elicits forced mounting (FM) and aggressive behavior (AB) towards the non-receptive female to different degrees, which can be scored. In a series of experiments we can show that SxA behavior is a relatively stable trait in rats and correlates positively with sexual motivation. Rats with innate abnormal anxiety and aggressive behavior also show abnormal SxA behavior. In addition, central infusion of oxytocin moderately inhibits AB, but increases FM. Finally, we identified the agranular insular cortex to be specifically activated by SxA, and inhibition of this region mildly decreased AB during the SxAT. Altogether, the SxAT is a paradigm that can be readily implemented in behavioral laboratories as a valuable tool to find answers regarding the biological mechanisms underlying SxA in humans, as well as social decision-making in general.

Acute fluoxetine differently affects aggressive display in zebrafish phenotypes

Zebrafish have been introduced as a model organism in behavioral neuroscience and biological psychiatry, increasing the breadth of findings using fish to study the neurobiology of aggression. Phenotypic differences between leopard and longfin zebrafish were exploited in order to elucidate the role of phasic serotonin in aggressive displays on this species. The present study revealed differences in aggressive display between leopard and longfin zebrafish, and a discrepant effect of acute fluoxetine in both populations. In mirror-induced aggression, leopard animals showed higher display latencies than longfin, as well as lower display duration and frequency (Experiment 1). Moreover, 2.5 mg/kg fluoxetine decreased the duration and frequency of display in longfin, but not leopard; and 5 mg/kg fluoxetine increased display frequency in leopard, but not longfin (Experiment 2). It is suggested that zebrafish from the longfin phenotype show more aggressive motivation and readiness in the mirror-induced aggression test that leopard, and that acute fluoxetine increases aggression in leopard and decreased it in longfin zebrafish.

Integrative focus on dynamic motor patterns and age hierarchy in the expression of aggression

In this study, we analyzed the dynamic motor patterns of attack or defense and age hierarchy to investigate aggression in African mole-rats Cryptomys foxi and the house mouse Mus musculus. The objective is to verify if the social order of dominance is associated with age hierarchy within the social group. Using the resident-intruder experimental model, we created a series of dyadic encounters that comprised of a standard adult mouse or rat paired with groups of aggressive and hierarchically age-ranked small animals in a territorial aggression test. Our results indicate that though the adult animals displayed the highest level of aggression, indicating their dominant status, there was no age-related hierarchical formation in the expression of aggression. In the non-territorial aggression test in which rats or mice were grouped together, animals displayed low levels of aggression compared to the territorial test and no hierarchical age-related order. These results indicate that the magnitude of aggression expressed by animals in the social group, based on their motor patterns of attack and defense, seem to depend on individual competitive strategies in reaction to various environmental challenges and not necessarily on age hierarchy.

Psychological Profile in Patients with Stages I and II Breast Cancer: Associations of Psychological Profile with Tumor Biological Prognosticators

We have earlier shown that breast cancer patients with moderately or well differentiated tumors seem to be able to inhibit stress evoked from anger in a successful manner, while those with poorer prognosis do not. We now report a study with an enlarged group of patients, investigating associations between tumor biological factors and psychological profile. 129 patients with Stages I and II breast cancer undergoing adjuvant radiation therapy were interviewed and tested with three projective personality tests assessing attitude to aggression and coping with stress and anxiety. Creative functioning was also tested. Patients with Stage I (smaller) tumors reported a “fighting spirit” attitude toward the disease, but they also showed depressive reaction patterns. Moreover, if the patient could successfully avoid or inhibit the stress evoked from perceiving an aggressive motif in the picture shown in the aggression test, the tumor biological situation was better. Patients who did not inhibit stress reactions on the aggression test and also on the anxiety test had a poorer tumor biological situation. Surprisingly, low speed of tumor cell proliferation (DNA S-phase fraction) correlared with high scores on the creativity test. Successful denial or inhibition of stress evoked by aggression combined with a creative, flexible attitude was associated with a better tumor biological situation.