Chronic stress, cyclic 17β-estradiol, and daily handling influences on fear conditioning in the female rat

A. N. Hoffman, Charles E. Armstrong, Jeffery J. Hanna, Cheryl Conrad

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

Chronic stress and estrogens alter many forebrain regions in female rats that affect cognition. In order to investigate how chronic stress and estrogens influence fear learning and memory, we ovariectomized (OVX) female Sprague-Dawley rats and repeatedly injected them (s.c.) with 17β-estradiol (E, 10 μg/250. g or sesame oil vehicle, VEH). Concurrently, rats were restrained for 6. h/d/21. d (STR) or left undisturbed (CON). Rats were then fear conditioned with 4. tone-footshock pairings and then after 1. h and 24. h delays, given 15. tone extinction trials. Regardless of E treatment, chronic stress (VEH, E) facilitated freezing to tone during acquisition and extinction following a 1. h delay, but not during extinction after a 24. h delay. E did not influence freezing to tone during any phase of fear conditioning for either the control or chronically stressed rats, but did influence contextual conditioning that may have been carried predominately by the STR group. In the second experiment, we investigated " handling" influences on fear conditioning acquisition, given the disparate findings from the current study and previous work (Baran, Armstrong, Niren, & Conrad, 2010; Baran, Armstrong, Niren, Hanna, & Conrad, 2009). Female rats remained gonadally-intact since E did not influence tone fear conditioning. Indeed, brief daily handling (1-3. m/d/21. d) facilitated acquisition of fear conditioning in chronically stressed female rats, and either had no effect or slightly attenuated fear conditioning in controls. Thus, chronic stress impacts amygdala-mediated fear learning in both OVX- and gonadally-intact females as found previously in males, with handling significantly influencing these outcomes.

Original languageEnglish (US)
Pages (from-to)422-433
Number of pages12
JournalNeurobiology of Learning and Memory
Volume94
Issue number3
DOIs
StatePublished - Oct 1 2010

Keywords

  • Amygdala
  • Chronic stress
  • Estrogen
  • Extinction
  • Fear conditioning
  • Handling
  • Ovariectomy
  • Restraint

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Cognitive Neuroscience
  • Behavioral Neuroscience

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