Oxytocin Reduces Background Anxiety in a Fear-Potentiated Startle Paradigm

Neuropsychopharmacology

Galen Missig1, Luke W Ayers1, Jay Schulkin2 and Jeffrey B Rosen1

  1. 1Department of Psychology, Behavioral Neuroscience Program, University of Delaware, Newark, DE, USA
  2. 2Department of Neuroscience, Georgetown University, Washington, DC, USA; Behavioral Endocrinology Section, National Institute of Mental Health, Bethesda, MD, USA; Research Department, American College of Obstetricians and Gynecologists, Washington, DC, USA

Correspondence: Professor JB Rosen, Department of Psychology, Behavioral Neuroscience Program, University of Delaware, 108 Wolf Hall, Newark, DE 19716, USA. Tel: +1 302 831-4209; Fax: +1 302 831-3645; E-mail: jrosen@udel.edu

Received 10 May 2010; Revised 8 August 2010; Accepted 9 August 2010; Published online 15 September 2010.

Abstract

Oxytocin reportedly decreases anxious feelings in humans and may therefore have therapeutic value for anxiety disorders, such as post-traumatic stress disorder (PTSD). As PTSD patients have exaggerated startle responses, a fear-potentiated startle paradigm in rats may have face validity as an animal model to examine the efficacy of oxytocin in treating these symptoms. Oxytocin (0, 0.01, 0.1, or 1.0 μg, subcutaneously) was given either 30 min before fear conditioning, immediately after fear conditioning, or 30 min before fear-potentiated startle testing to assess its effects on acquisition, consolidation, and expression of conditioned fear, respectively. Startle both in the presence and absence of the fear-conditioned light was significantly diminished by oxytocin when administered at acquisition, consolidation, or expression. There was no specific effect of oxytocin on light fear-potentiated startle. In an additional experiment, oxytocin had no effects on acoustic startle without previous fear conditioning. Further, in a context-conditioned test, previous light-shock fear conditioning did not increase acoustic startle during testing when the fear-conditioned light was not presented. The data suggest that oxytocin did not diminish cue-specific conditioned nor contextually conditioned fear, but reduced background anxiety. This suggests that oxytocin has unique effects of decreasing background anxiety without affecting learning and memory of a specific traumatic event. Oxytocin may have antianxiety properties that are particularly germane to the hypervigilance and exaggerated startle typically seen in PTSD patients.

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Author: Leslie Carol Botha

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