The Effect of Aversive Early Experience on the Behavioral and Biological Fear Response in Rats

Abstract

The effects of both positive and negative early life experiences on subsequent emotional reactivity are a major focus in current research on the etiology of neuropsychiatric disorders. Specifically, traumatic events, particularly when combined with genetic vulnerability, may exert a profound influence on the future psychological and biological development of an organism. In this study our lab examined the effects of a traumatic event early in life, maternal separation, on the future biobehavioral reactivity in animals with (borderline hypertensive rats) and without (Sprague-Dawley) a genetic predisposition for cardiovascular and emotional reactivity. Subjects were separated from the litter for two hours from post-natal days 1 through 14. Beginning at 6 weeks of age, anxiety-like behavior and locomotor activity was tested by elevated plus maze and open field, respectively. One day following implantation of an arterial catheter, fear conditioning was used to produce an aversive emotional event (lO pairings an environmental cue (tone) followed by a brief lmA footshock). 24 hours later, emotional (e.g., freezing, vocalizations) and biological (e.g., blood pressure, corticosterone) responses were assessed in all subjects in response to re-exposure to the context (original context) and cue (altered context + tone). Results could provide an explanation for some of the differences between those susceptible to neuropsychiatric disorders like PTSD and those who are resistant. Results may also be used to expand upon the emerging body of research concerning the link between cardiovascular disease and PTSD.