Conspecific Interactions in Adult Laboratory Rodents: Friends or Foes?

Abstract

Interactions between adult conspecifics, including sexual behaviors, affiliation, and aggression are crucial for the well-being, survival, and reproduction of mammals. This holds true for any mammalian species, but certainly for humans: An inability to optimally navigate the social system can have a strong negative impact on physical and mental health. Translational rodent models have been used for decades to unravel the neural pathways and substrates involved in normal and abnormal conspecific interactions. Researchers in the field of translational social neuroscience face a double challenge: Not only do they need to pay considerable attention to the behavioral ecology of their model species or their ancestors, they also have to expect a relatively large variability in behavior and adjust their experimental design accordingly. In this chapter, we will lay out traditional and novel rodent models and paradigms to study sexual, affiliative, and aggressive interactions among adult conspecifics. We will discuss the merits and main findings and briefly consider the most promising novel directions. Finally, we review the modulatory involvement of two major players in mammal social interaction: the central oxytocin and vasopressin system.

Concerted but segregated actions of oxytocin and vasopressin within the ventral and dorsal lateral septum determine female aggression

“…In detail, the display of high aggression by IST females during the FIT was accompanied by elevated OXT release within the vLS, which was also reflected by higher OXT levels in their CSF. Together with the fact that central OXT release correlated with aggression, this indicates the involvement of septal OXT in the high aggression displayed by IST rats, which we further confirmed by complementary pharmacological, chemogenetic and optogenetic approaches: OXT and AVP have been repeatedly described as important neuromodulators of social behaviors in rodents, acting either synergistically or antagonistically depending on the social context and sex 8,9,22,24,36,43 . In males, reduced aggression has been reported in rats after i.c.v.…”

“…In contrast, the few studies on OXT-effects on female aggression rather revealed pro-aggressive or antisocial effects, for example in female rhesus monkeys 44 , non-lactating women 8,45 , and in lactating female rats 18,33 . Although the factors motivating the display of aggression and its severity likely differ in lactating versus virgin females 5,33,46,47 , we should highlight that from an evolutionary point of view, co-opting the same neuropeptidergic systems for promoting aggression in lactating females to protect the offspring, and in virgin females to protect their territory, or to get access to resources, makes sense; especially knowing that high activity of the brain OXT system reflected by elevated neuropeptide synthesis, release and binding 18,24,33,36 is known to underlie maternal aggression 24,33,36,48 . Further evidence for a sex-specific effect of OXT on social behavior comes from studies on social motivation, where OXT is essential for naturally occurring social preference behavior in male rats and mice , but not in virgin female rats 50 .…”

“…Next, we investigated the role of oxytocin (OXT) and arginine vasopressin (AVP) in female aggression. Both neuropeptides have been associated with various social behaviors including aggression in males and lactating females [17][18][19][20][21][22][23][24] , and are known to be affected by social isolation in a sex-dependent manner 11,13 . In this context, we hypothesized that the effects of OXT and AVP on female aggression are predominantly mediated in the lateral septum (LS) -a target region for neuropeptide actions 24 , known to suppress aggression in both sexes 10,25 .…”

“…Although several pieces of evidence point towards the gating role of the LS in aggression, the underlying mechanisms, especially the involvement of septal OXT and AVP in female aggression, are still unknown. The release of both neuropeptides in the LS has been tied to various social behaviors, including intermale aggression, although the results are somewhat conflicting 24 . For example, in male Wistar rats attenuated 21 as well as increased 22 release of AVP have been described during the display of abnormal and high 31 levels of aggression, respectively.…”

Oxytocin and Social Relationships: From Attachment to Bond Disruption

“…In addition to its role in pair bonding, OT is released centrally during pro-social interactions thereby regulating other social behaviors, e.g., social recognition, social memory, parental behavior, as mainly demonstrated in rodents (Bosch and Neumann 2012; Lukas and Neumann 2013; Dumais and Veenema 2016; Lukas and de Jong 2017). In male and female prairie voles, OT acting on the anterior cingulate cortex, a region implicated in empathy in humans (Lamm et al 2011), regulates empathy-based consoling behaviors (Burkett et al 2016).…”