Elevated Fos-like immunoreactivity in the brains of postpartum female prairie voles, Microtus ochrogaster

Pair Bond-Induced Affiliation and Aggression in Male Prairie Voles Elicit Distinct Functional Connectivity in the Social Decision-Making Network

Complex social behaviors are governed by a neural network theorized to be the social decision-making network (SDMN). However, this theoretical network is not tested on functional grounds. Here, we assess the organization of regions in the SDMN using c-Fos, to generate functional connectivity models during specific social interactions in a socially monogamous rodent, the prairie voles (Microtus ochrogaster). Male voles displayed robust selective affiliation toward a female partner, while exhibiting increased threatening, vigilant, and physically aggressive behaviors toward novel males and females. These social interactions increased c-Fos levels in eight of the thirteen brain regions of the SDMN. Each social encounter generated a distinct correlation pattern between individual brain regions. Thus, hierarchical clustering was used to characterize interrelated regions with similar c-Fos activity resulting in discrete network modules. Functional connectivity maps were constructed to emulate the network dynamics resulting from each social encounter. Our partner functional connectivity network presents similarities to the theoretical SDMN model, along with connections in the network that have been implicated in partner-directed affiliation. However, both stranger female and male networks exhibited distinct architecture from one another and the SDMN. Further, the stranger-evoked networks demonstrated connections associated with threat, physical aggression, and other aversive behaviors. Together, this indicates that distinct patterns of functional connectivity in the SDMN can be detected during select social encounters.

Genetics of aggression in voles

Prairie voles (Microtus ochrogaster) are socially monogamous rodents that form pair bonds-a behavior composed of several social interactions including attachment with a familiar mate and aggression toward conspecific strangers. Therefore, this species has provided an excellent opportunity for the study of pair bonding behavior and its underlying neural mechanisms. In this chapter, we discuss the utility of this unique animal model in the study of aggression and review recent findings illustrating the neurochemical mechanisms underlying pair bonding-induced aggression. Implications of this research for our understanding of the neurobiology of human violence are also discussed.

Features of the expression of the c-Fos gene along the rostrocaudal axis of the hippocampus in common voles after rapid training to solve a spatial task

The level of expression of the c-Fos protein in neurons was used as a measure of the activation of transcription in the hippocampus of common voles (Microtus arvalis Pall.) after rapid spatial training. Stained Fos-positive cells were counted on 20 brain sections along the rostrocaudal axis of the hippocampus. Voles were trained to find the exit to their home cages through one of the arms of a modified eight-arm radial maze (using a 2-h series of six trials on one day). Animals were initially trained to leave the home cage via an arm not connected to the maze. Voles of the "active" control group were passed through the isolated arm into the home cage six times on the experimental day. Animals for the "passive" control for c-Fos levels were collected from their home cages. Significant increases in c-Fos expression in voles trained in the maze and the active control group, as compared with passive controls, were seen in all areas studied (hippocampal fields CA1 and CA3 and the dentate fascia). At the same time, a significant increase in the number of c-Fos-positive neurons in voles trained in the maze, as compared with the active controls, was noted only in the caudal hippocampus, no differences being seen in the rostral part. The greatest levels of activation were seen in the dentate fascia and field CA3. These results provide evidence for the heterogeneous functioning of the hippocampus along the rostrocaudal axis during training of voles to solve a spatial task.