Social facilitation of wound heating

It is well documented that psychological stress impairs wound healing in humans and rodents. However, most research effort into influences on wound healing has focused on factors that compromise, rather than promote, heating. In the present study, we determined if positive social interaction, which influences hypothalamic-pituitary-adrenal (HPA) axis activity in social rodents, promotes wound heating. Siberian hamsters received a cutaneous wound and then were exposed to immobilization stress. Stress increased cortisol, concentrations and impaired wound heating in isolated, but not socially housed, hamsters. Removal of endogenous cortisol via adrenalectomy eliminated the effects of stress on wound healing in isolated hamsters. Treatment of isolated hamsters with oxytocin (OT), a hormone released during social contact and associated with social bonding, also blocked stress-induced increases in cortisol concentrations and facilitated wound heating. In contrast, treating socially housed hamsters with an OT antagonist delayed wound healing. Taken together, these data suggest that social interactions buffer against stress and promote wound heating through a mechanism that involves OT-induced suppression of the HPA axis. The data imply that social isolation impairs wound heating, whereas OT treatment may ameliorate some effects of social isolation on health. (C) 2003 Elsevier Ltd. All rights reserved.