Physiology, endocrinology and chemical communication in aggressive behaviour of fishes

Exploring the influence of stress on aggressive behavior and sexual function: Role of neuromodulator pathways and epigenetics

Stress is a complex and multifaceted phenomenon that can significantly influence both aggressive behavior and sexual function. This review explores the intricate relationship between stress, neuromodulator pathways, and epigenetics, shedding light on the various mechanisms that underlie these connections. While the role of stress in both aggression and sexual behavior is well-documented, the mechanisms through which it exerts its effects are multifarious and not yet fully understood. The review begins by delving into the potential influence of stress on the Hypothalamic-Pituitary-Adrenal (HPA) axis, glucocorticoids, and the neuromodulators involved in the stress response. The intricate interplay between these systems, which encompasses the regulation of stress hormones, is central to understanding how stress may contribute to aggressive behavior and sexual function. Several neuromodulator pathways are implicated in both stress and behavior regulation. We explore the roles of norepinephrine, serotonin, oxytocin, and androgens in mediating the effects of stress on aggression and sexual function. It is important to distinguish between general sexual behavior, sexual motivation, and the distinct category of "sexual aggression" as separate constructs, each necessitating specific examination. Additionally, epigenetic mechanisms emerge as crucial factors that link stress to changes in gene expression patterns and, subsequently, to behavior. We then discuss how epigenetic modifications can occur in response to stress exposure, altering the regulation of genes associated with stress, aggression, and sexual function. While numerous studies support the association between epigenetic changes and stress-induced behavior, more research is necessary to establish definitive links. Throughout this exploration, it becomes increasingly clear that the relationship between stress, neuromodulator pathways, and epigenetics is intricate and multifaceted. The review emphasizes the need for further research, particularly in the context of human studies, to provide clinical significance and to validate the existing findings from animal models. By better understanding how stress influences aggressive behavior and sexual function through neuromodulator pathways and epigenetic modifications, this research aims to contribute to the development of innovative protocols of precision medicine and more effective strategies for managing the consequences of stress on human behavior. This may also pave way for further research into risk factors and underlying mechanisms that may associate stress with sexual aggression which finds application not only in neuroscience, but also law, ethics, and the humanities in general.

Bile acids as putative social signals in Mozambique tilapia (Oreochromis mossambicus)

Chemical cues provide potential mates with information about reproductive status and resource-holding potential. In the Mozambique tilapia (Oreochromis mossambicus), males can distinguish female reproductive status through chemical cues, and accessibility of males to females depends on their position in the hierarchy, determined in part by chemical cues. Here, we hypothesized that tilapia faecal cues are attractive to conspecifics once released into the water. C18 solid-phase extracts of faeces from dominant males and pre-ovulatory females evoked stronger olfactory epithelium electrical responses (EOG) than, respectively, subordinate males and post-spawning females. Mass spectrometry of the reverse-phase C18 high-performance liquid chromatography fractions of these extracts with highest EOG, identified by amino acids and bile acids. Faeces from pre-ovulatory females contain significantly higher concentrations of cholic acid (CA) and taurocholic acid (TCH) than both post-spawning females and males. A pool of amino acids had no effect on aggression or attraction in males. However, males were attracted to the scent of pre-ovulatory female faeces, as well as CA and TCH, when applied separately. This attraction was accompanied by increased digging behaviour compared to the odour of post-spawning females. CA and TCH exert their action through separate receptor mechanisms. These findings are consistent with a role for faeces - and bile acids therein - in chemical communication in this species, acting as an attractant for males to reproductive females.

Evaluation of dietary food intakes and anthropometric measures in middle-aged men with aggressive symptoms

BACKGROUND

Aggression is one of the most prevalent behavioral disorders in men.

OBJECTIVE

This study aimed to assess the possible association between dietary intake of food groups and aggression in middle-aged married men.

METHODS

This case-control study included 336 participants (168 men with aggressive behaviors and 168 healthy controls) aged 35-55 years. Demographic information was collected using a socio-demographic questionnaire. A food frequency questionnaire was used to investigate the diet group intake last year. Based on the normality of the data distribution, Independent t-tests and Mann-Whitney tests were used to compare quantitative variables between the two groups. Categorical variables were compared between cases and controls using the Chi-squared test. Logistic regression analysis was used to examine the possible association between food intake and aggression.

RESULTS

Compared to controls, aggressive men had significantly higher mean weight, height, and waist circumference (WC), p = 0.007, p = 0.001, and p = 0.043, respectively. After adjusting WC, energy intake, and educational level, in Model 1, intake of milk, cheese, poultry, red meat, legumes, egg, fruits, and vegetables had a significant protective role on the occurrence of aggression, (Odd Ratio (OR) = 0.36; 95% (Confidence Interval (CI) = 0.204, 0.670; P = 0.001), (OR = 0.440; 95% CI = 0.284, 0.781; P = 0.005), (OR = 0.621; 95% CI = 0.284, 0.781; P = 0.046), (OR = 0.358; 95% CI = 0.198, 0.647; P = 0.001), (OR = 0.434; 95% CI = 0.243, 0.773; P = 0.005), (OR = 0.411; 95% CI = 0.229, 0.736; P = 0.003), (OR = 0.332; 95% CI = 0.180, 0.614; P < 0.001), (OR = 0.310; 95% CI = 0.168, 0.572; P < 0.001), respectively.

CONCLUSIONS

Lower WC and a diet containing high-quality protein, fruits, and vegetables can have a protective role against aggression and are recommended for men with an aggressive mood. This diet can affect plasma levels of tryptophan and, therefore, brain levels of serotonin.

Follicular complex may predict reproductive tactics in siluriform fishes

In this study, we evaluated the morphology and morphometry of the layers that make up the follicular complex surrounding mature oocytes in the six fish species Auchenipterichthys longimanus, Ageneiosus ucayalensis, Hypophthalmus marginatus, Baryancistrus xanthellus, Panaqolus tankei and Peckoltia oligospila, belonging to the order Siluriformes, which inhabit the Amazon basin. On the basis of the morphology and thickness of the layers of the follicular complex, the species were divided into two groups: 1- A. longimanus, A. Ucayalensis and H. marginatus and 2 - B. xanthellus, P. tankei and P. oligospila. The total thickness of the layers that make up the follicular complex showed a difference between type III and IV oocytes for all species of each group. Differences in the theca layer, follicular cells and zona radiata between species and between groups were submitted to statistical analysis. Morphologically, group 1 showed columnar follicular cells and thin zona radiata. Meanwhile, group 2 displayed a layer of cuboidal-shaped follicular cells layer and thicker zona radiata. These differences may be related to the environment and reproductive behaviors, as group 1 migrates without parental care and has eggs that are generally smaller and abundant. While group 2, represented by loricariidae, inhabit lotic environments, have reproductive tactics of parental care and eggs that are generally large and in small numbers. Therefore, we can infer that the follicular complex in mature oocytes can predict the reproductive tactics of the species.

Discovery of 16-Androstenes (Androstenone and Androstenol), Their Synthesis Pathway, and Possible Role in Reproduction of Mouse Deer (Moschiola indica)

We discovered odorous 16-androstenes (Androstenone and Androstenol) in endangered mouse deer during a captive breeding program. This study examined the molecular characteristics, their synthesis pathway, and the possible functional role of these compounds in the reproduction of mouse deer. CYP17A1 and CYB5 genes were cloned and expressed in HEK-293, COS-7 cell lines, and gonads of mouse deer to investigate the CYP17A1 gene’s andien-β-synthase activity towards the synthesis of 16-androstenes in mouse deer. An enzyme immunoassay was further developed and standardized to measure fecal androstenone during the reproductive cycles of mouse deer. Results showed that the mouse deer CYP17A1 gene possesses andien-β-synthase activity and could transform pregnenolone into 5,16-androstadien-3β-ol. The expression of the CYP17A1 gene upregulated in the testis and ovary compared to other tissues in mouse deer. Significantly elevated androstenone and estrogens were recorded prior to delivery and postpartum estrus/mating in mouse deer. Further, there were weak correlations between fecal androstenone and estrogens/androgens in mouse deer during the breeding season. These findings suggest that androstenone probably plays a role in the reproductive activities of mouse deer. This knowledge can be used for captive breeding programs of mouse deer in India and elsewhere.

Social effects on AVT and CRF systems

Stress and aggression have negative effects on fish welfare and productivity in aquaculture. Thus, research to understand aggression and stress in farmed fish is required. The neuropeptides arginine-vasotocin (AVT) and corticotropin-releasing factor (CRF) are involved in the control of stress and aggression. Therefore, we investigated the effect of agonistic interactions on the gene expression of AVT, CRF and their receptors in juvenile rainbow trout (Oncorhynchus mykiss). The social interactions lead to a clear dominant-subordinate relationship with dominant fish feeding more and being more aggressive. Subordinate fish had an upregulation of the AVT receptor (AVT-R), an upregulation of CRF mRNA levels, and higher plasma cortisol levels. The attenuating effect of AVT on aggression in rainbow trout is proposed to be mediated by AVT-R, and the attenuating effect of the CRF system is proposed to be mediated by CRF.