title: Heat exposure in female rats elicits abnormal fear expression and cellular changes in prefrontal cortex and hippocampus.
abstract: Despite a twofold higher prevalence of fear-related disorders in women, the neurobiological factors that modulate and drive fear expression are rarely studied in female animals. Fear conditioning and extinction are useful tools for dissecting these mechanisms, and here we tested the effects of environmental manipulations - four days of exposure to 31°C temperatures in the animal housing facility - on fear learning and memory exclusively in female rats. We found that heat exposure disrupted freezing to tone during fear conditioning, and elicited enhanced freezing during extinction and extinction retrieval. We also performed immunohistochemistry for c-fos expression in the infralimbic (IL) and prelimbic (PL) regions of the prefrontal cortex during extinction retrieval, and found that heat exposure induced a switch from IL-dominated activity to PL-dominated activity. Finally, morphological analysis of spines in hippocampal CA3 neurons revealed an increase in spine head diameter in heat-exposed animals, which may partly underlie the persistent freezing observed in these animals. Together, our data show that heat exposure can induce changes at behavioral, physiological, and structural levels, and add to a woefully lacking body of literature on fear processes in female animals.
authors.affiliation: Laboratory of Neuroanatomy and Behavior, Department of Psychology, Northeastern University, Boston, MA 02115, United States.
authors.forename: Tina M
authors.initials: TM
authors.lastname: Gruene
authors.affiliation: Laboratory of Neuroanatomy and Behavior, Department of Psychology, Northeastern University, Boston, MA 02115, United States.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lipps
authors.affiliation: Laboratory of Neuroanatomy and Behavior, Department of Psychology, Northeastern University, Boston, MA 02115, United States.
authors.forename: Colin D
authors.initials: CD
authors.lastname: Rey
authors.affiliation: Laboratory of Neuroanatomy and Behavior, Department of Psychology, Northeastern University, Boston, MA 02115, United States.
authors.forename: Anna
authors.initials: A
authors.lastname: Bouck
authors.affiliation: Laboratory of Neuroanatomy and Behavior, Department of Psychology, Northeastern University, Boston, MA 02115, United States. Electronic address: r.shansky@neu.edu.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Shansky
mesh_terms: D000818:Animals; D056654:CA3 Region, Hippocampal / Q000473:pathology; D003214:Conditioning, Classical / Q000502:physiology; D005108:Extinction, Psychological / Q000502:physiology; D005239:Fear / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006358:Hot Temperature / Q000009:adverse effects*; D017397:Prefrontal Cortex / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D020318:Rats, Long-Evans
chemical_list: D016760:Proto-Oncogene Proteins c-fos
keywords: Dendritic spines; Extinction; Fear conditioning; Females; Hippocampus; Prefrontal cortex