Oxytocin and vasopressin modulation of the neural correlates of motivation and emotion: results from functional MRI studies in awake rats

Abstract

Oxytocin and vasopressin modulate a range of species typical behavioral functions that include social recognition, maternal-infant attachment, and modulation of memory, offensive aggression, defensive fear reactions, and reward seeking. We have employed novel functional magnetic resonance mapping techniques in awake rats to explore the roles of these neuropeptides in the maternal and non-maternal brain. Results from the functional neuroimaging studies that are summarized here have directly and indirectly confirmed and supported previous findings. Oxytocin is released within the lactating rat brain during suckling stimulation and activates specific subcortical networks in the maternal brain. Both vasopressin and oxytocin modulate brain regions involved unconditioned fear, processing of social stimuli and the expression of agonistic behaviors. Across studies there are relatively consistent brain networks associated with internal motivational drives and emotional states that are modulated by oxytocin and vasopressin. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Keywords: Addiction; Aggression; Aggressive behavior; Anxiety; Autism; Awake rat imaging; BOLD fMRI; Fear; Functional MRI; Maternal attachment; Maternal rat; Oxytocin; Rat; Vasopressin.

Figure 1. Neural Circuitry of High Density OT Receptor Binding Sites

The 3D color model on the top depicts the brain areas in the rat with a high density of OT receptor. These areas are coalesced into a single volume (yellow) within a translucent shell of the brain, as shown in the lower 3D images for ICV. Areas colored red are the localization of activated voxels representing the composite average of nine rat brain fMRI scans. Once fully registered, and segmented, the statistical responses for each animal are averaged on a voxel-by-voxel basis. The averaged voxels that are significantly different from baseline, and exceed a 2.0% threshold, are show in their appropriate spatial location. The 2D images appearing to the right of each 3D image show the location of interpolated voxels of positive BOLD activation registered onto coronal sections of the segmented rat atlas. The approximate location of these brain slices are depicted by the black lines shown in the 3D ICV image.