Secondary pharmacological prevention of PTSD: Therapeutic implications of a translational model

Abstract

"Significance facilitates remembrance" (McGaugh 1990). Millions of Asians arelikely to remember in vivid detail where they were and what they were doing on themorning of 26 December 2004, when the disastrous tsunami struck the shores of theIndian Ocean. In contrast, few of these persons are likely to remember in any detailwhere they were and what they were doing on the morning of 19 December, only aweek earlier. We are more likely to remember significant life events than trivialones, and this is surely the result of natural selection. Suppose a hypothetical primitivehominid decided to take a new route to a watering hole, and on her way sheencountered a crocodile. Should she fail to remember in the future that a crocodileinhabited that route, she would be more likely to take the same route again and beeliminated from the gene pool!Evolution appears to have enabled significance to facilitate remembrance bymeans of modulatory effects exerted by neurohormones on the consolidation ofmemory traces, or alternately stated, on the acquisition of conditioned emotionalresponses. Because emotionally arousing events mobilize neurohormones, facilitationof learning by these hormones amounts to a mechanism whereby the intensityof the unconditioned emotional response to an arousing event regulates the strengthof the resultant conditioned response. Evolution favors parsimony; if it can achievetwo adaptations through one mechanism, it often will. In the above hypotheticalexample, the same adrenaline (or epinephrine, EPI) that enabled our primitive hominidto run away from the crocodile acted in her brain to strengthen her memory ofthe frightful encounter.