Evaluating the stress system of the grieving brain: corticotropin-releasing factor receptors and partner loss in coyotes (Canis latrans)

Forming social bonds is fundamental in helping us foster connections with others. The loss of a loved one often results in grief, stress, and loneliness, and the stress response system of the body has been implicated in the physiological symptoms associated with grieving. Corticotropin releasing factor (CRF) is the hormone that initiates the stress response in the body and acts at two different receptor subtypes CRF receptor (CRFR)1 and CRFR2. Many studies on CRF and social loss have been conducted in monogamous prairie voles, but studies in longer-lived monogamous mammals could improve understanding of the effects of losing pair bonds. A monogamous mating system and stable pair bonding behavior exhibited by coyotes (Canis latrans) make them an appropriate animal model to study social bonds and social loss. Our goal of this larger study was to map CRFR1 and CRFR2 in the coyote brain using a competitive binding approach and to quantify CRFR levels in both widowed and paired female coyotes, allowing us to determine if CRFRs densities changed in response to partner loss. The results of our mapping study showed that the olfactory system, hippocampus, and amygdala were sites of action of CRFRs. Region-specific differences in CRFR1 and CRFR2 binding were observed after partner loss. Specifically, elevated CRFR1 and CRFR2 binding were detected in widows in the olfactory bulb and olfactory tubercle respectively, suggesting a potential role of the olfactory system in regulating the brain’s response to social loss in coyotes.