Behavioral responses to emotional challenges in female rats living in a seminatural environment: The role of estrogen receptors

Abstract

Estrogen receptors (ERs) are involved in sexual as well as non-sexual behaviors. In the present study we assessed the effects of stimuli inducing positive or negative affect on sociosexual, exploratory and fear-related behaviors of female rats housed in groups ( 4females, 3 males) in a seminatural environment. Ovariectomized females were treated with oil, 17β-estradiol benzoate (EB, 18 μg/kg), the ERα agonist propylpyrazoletriol (PPT), or the ERβ agonist diarylpropionitrile (DPN) (both 2 x 10 mg/rat). On the test day, the females were exposed to a sequence of events consisting of lavender odor, Mozart's Sonata for Two Pianos K448, chocolate pellets, white noise and fox odor (2,3,5-Trimethyl-3-thiazoline, TMT). All these events are known to induce positive or negative affect. Behavior was carefully observed from the video record. White noise suppressed sexual behaviors and reduced the time spent in the open area of the environment. TMT had no consistent effect whereas exposure to music caused avoidance of the open area. Exposure to chocolate increased exploratory and social behavior. Lavender odor enhanced exploratory behavior. PPT and EB stimulated sexual behaviors, whereas DPN was ineffective. Co-occurrence analyses of the sequence of behavioral patterns revealed that PPT and EB consistently belonged to clusters different from oil and DPN, whereas DPN was separate from oil only under fear-inducing experimental conditions. These data, from a procedure with external validity, confirm that the ERα is crucial for sexual behaviors, that these behaviors are reduced under stressful conditions, and that the ERβ may have some role in fear-related behaviors.

Male and female immediate fear reaction to white noise in a semi‐natural environment: A detailed behavioural analysis of the role of sex and oestrogen receptors

“…38,67 The immediate response to the noise is similar to the sustained response (ie, behaviour observed during a continuous 15-minute exposure) reported in earlier studies. 26,27 This suggests Visits to the open area recovered more slowly, with recovery needing more than 5 minutes. 28 The latter observations indicate that the white noise did not cause a lasting fear or anxiety reaction.…”

“…The floor of the semi-natural environment was disinfected and cov- In a previous study 27 , we focused on sustained effects of emotional stimuli without analysing immediate effects of said stimuli.…”

“…Experiments previously conducted in our laboratory showed that white noise was highly aversive to the rats, efficiently eliciting classical fear-and anxiety-related behaviours. [26][27][28] These and other anxiety studies analysed behaviour expressed over the entire duration of the test (ie, sustained anxiety). Immediate fear and anxiety reactions (ie, phasic anxiety) might be more informative and are worthy of special attention.…”

“…24,25 Previous studies conducted in our laboratory have looked into the expression of fear in females rats hosted in a semi-natural environment 26 and more specifically into the differential role of oestrogen receptors in emotional responses in this environment. 27,28 Indeed, the variability in male and female fear and anxiety-related behaviours is considered to rely, at least partly, on the main female hormone oestradiol. 29 This steroid modulates behaviour differently depending on the environmental context.…”

“…28 By contrast, activation of ERβ has consistently led to anxiolytic effects in the elevated plus-maze 33,[35][36][37] and in the open field. 33 In a semi-natural environment, females treated with an ERβ agonist showed a distinct profile in response to aversive situations, 27 whereas females with a reduced number of ERβ in the central amygdala showed a pattern of increased anxiety, including increased risk assessment and decreased food consumption. 28 Thus, oestradiol plays an important role in the modulation of fear and anxiety reactions in females, through the differential activation of ERα and ERβ, which could partly explain the sex difference in anxiety prevalence.…”