title: Acute escitalopram but not contextual conditioning exerts a stronger "anxiogenic" effect in rats with high baseline "anxiety" in the acoustic startle paradigm.
abstract: BACKGROUND
  Acute administration of selective serotonin reuptake inhibitors (SSRIs) may enhance anxiety in humans, those with anxiety disorders being more susceptible than others. Fear-conditioned or unconditioned acoustic startle and freezing are common measures of fear and/or "anxiety" in rodents that may be used to study this effect of SSRIs preclinically.
  
  
  OBJECTIVE
  Our aim was to shed further light on the effect of acute administration of an SSRI, escitalopram (10 mg/kg), on startle and freezing in the absence or presence of prior contextual conditioning. Repeated testing also enabled us to evaluate (i) if there are stable inter-animal variations with respect to these parameters in a batch of outbred Wistar rats, (ii) the possible relationship between the two and (iii) if baseline behaviour predicts the response to escitalopram.
  
  
  RESULTS
  Inter-animal test-retest correlations were found for both startle and freezing at baseline, and the two parameters also correlated with each other. Both escitalopram and contextual conditioning increased freezing and startle but without exerting any synergistic effect. While animals displaying high startle at baseline showed higher susceptibility to respond to escitalopram, the effect of conditioning was more pronounced in those with low baseline startle.
  
  
  CONCLUSIONS
  The results support the usefulness of both conditioned and non-conditioned startle and freezing to capture an "anxiogenic" influence of SSRIs. Also, they suggest that baseline non-conditioned startle may predict this response in a manner reflecting the clinical situation in the sense that subjects with high baseline "anxiety" are particularly prone to respond with enhanced "anxiety" following acute SSRI administration.
authors.affiliation: Department of Pharmacology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Box 431, SE-405 30, Gothenburg, Sweden.
authors.forename: Robert
authors.initials: R
authors.lastname: Pettersson
authors.forename: Jakob
authors.initials: J
authors.lastname: Näslund
authors.forename: Staffan
authors.initials: S
authors.lastname: Nilsson
authors.forename: Elias
authors.initials: E
authors.lastname: Eriksson
authors.forename: S Melker
authors.initials: SM
authors.lastname: Hagsäter
mesh_terms: D000161:Acoustic Stimulation / Q000009:adverse effects*; D000818:Animals; D001007:Anxiety / Q000139:chemically induced* / Q000523:psychology*; D015283:Citalopram / Q000008:administration & dosage* / Q000009:adverse effects*; D005239:Fear / Q000187:drug effects / Q000523:psychology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013216:Reflex, Startle / Q000187:drug effects*; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage / Q000009:adverse effects
chemical_list: D015283:Citalopram; D017367:Selective Serotonin Reuptake Inhibitors