Sex Differences in Behavioral Responses during a Conditioned Flight Paradigm

Abstract

<jats:title>Abstract</jats:title><jats:p>Females exhibit greater susceptibility to trauma- and stress-related disorders compared to males; therefore, it is imperative to study sex differences in the mode and magnitude of defensive responses in the face of threat. To test for sex differences in defensive behavior, we used a modified Pavlovian fear conditioning paradigm that elicits clear transitions between freezing and flight behaviors within individual subjects. Female mice subjected to this paradigm exhibited higher percentages of freezing behavior compared to males, especially during the intertrial interval period. Female mice also exhibited more cued freezing in response to the conditioned stimuli in the last block of extinction training. Furthermore, there were sex differences in the expression of other adaptive behaviors during fear conditioning. Assaying rearing, grooming, and tail rattling behaviors during the conditioned flight paradigm yielded measurable differences across sessions and between males and females. Overall, these results provide insight into sex-dependent alterations in mouse behavior induced by fear conditioning.</jats:p><jats:sec><jats:title>Highlights</jats:title><jats:p><jats:list list-type="bullet"><jats:list-item><jats:p>Male and female mice do not differ in conditioned flight behavior.</jats:p></jats:list-item><jats:list-item><jats:p>Female mice exhibit more freezing behavior.</jats:p></jats:list-item><jats:list-item><jats:p>Rearing, self-grooming, and tail rattling behavior changes across days.</jats:p></jats:list-item><jats:list-item><jats:p>Male mice exhibit more rearing and grooming behavior.</jats:p></jats:list-item><jats:list-item><jats:p>Female mice exhibit more tail rattling behavior.</jats:p></jats:list-item></jats:list></jats:p></jats:sec>

Individual Differences in Conditioned Fear and Extinction in Female Rats

“…This is in contrast to the lack of male–female differences in freezing ( Gruene et al, 2015b ), but higher levels of darting, thought to be a type of escape behavior, seen in females compared to males during fear conditioning and extinction trials ( Gruene et al, 2015a ). Sex differences in freezing are also seen in paradigms that require discrimination between both fear and safety cues ( Clark et al, 2019 ; Greiner et al, 2019 ; Borkar et al, 2020 ) or fear generalization ( Jasnow et al, 2017 ), perhaps suggesting sex differences in the ability to discriminate fear and safety cues or environmental stimuli that might have influenced fear extinction in a novel context in our paradigm. Further, we selected a median split during extinction learning to separate the phenotypes for comparison to our studies in males ( Sharko et al, 2017 ; Kellis et al, 2020 ), and it clearly led to two phenotypes based on overall freezing, rearing, and 50 kHz USV differences between ER and EC groups.…”

“…Previous studies also report that females generally produce less freezing than their male counterparts during various stages of fear paradigms ( Maren et al, 1994 ; Pryce et al, 1999 ; Gupta et al, 2001 ; Wiltgen et al, 2001 ; Chang et al, 2009 ), and this diminished level of freezing might have blunted the separation between extinction phenotypes in our female population. In contrast, using a fear conditioning protocol that assesses both freezing and flight (escape) responses, females showed greater freezing than males, but no differences in flight responses ( Borkar et al, 2020 ). This is in contrast to the lack of male–female differences in freezing ( Gruene et al, 2015b ), but higher levels of darting, thought to be a type of escape behavior, seen in females compared to males during fear conditioning and extinction trials ( Gruene et al, 2015a ).…”

“…The understanding of individual differences in fear responses in females is also confounded by sex differences in phenotypic expression of fear. While Pavlovian fear conditioning and extinction in rodents are traditionally measured in terms of freezing, emerging studies show that females display a different repertoire of fear responses compared to their male counterparts ( LeDoux, 1994 ; Shumake et al, 2014 ; Gruene et al, 2015a , b ; Borkar et al, 2020 ). Female rodents usually exhibit less freezing than males during cued fear learning, conventionally understood as impaired learning, but this interpretation may be confounded by more recent data showing females exhibit darting responses to fear more often than males ( Baran et al, 2009 ; Gruene et al, 2015a ; Colom-Lapetina et al, 2019 ).…”

Effect of Estrous Cycle on Behavior of Females in Rodent Tests of Anxiety

“…For example, depending on strain and precise experimental protocol, no sex difference in contextual fear conditioning ( 208 ); stronger context fear conditioning and more generalization to a similar context have been reported in females compared to males ( 209 ), whilst extinction of conditioned freezing to a tone was faster in males than in females ( 210 ). Using a serial compound conditioned stimulus (tone and white noise that elicits clear transitions between freezing and flight behaviors within individual subjects) females exhibited more freezing behavior than males although there was no difference between the sexes in flight behavior ( 211 ).…”

Exogenous Flupirtine as Potential Treatment for CLN3 Disease

“…Chronic stress leads to increased corticosterone levels [ 31 ], as observed in WT male and female mice with respect to Cln3 Δex7/8 mice. Several studies elucidate that animals who do not experience stress show higher exploration, locomotion, and physical activity in an open field test, as a reaction to an unknown environment [ 32 , 33 ]. Therefore, the markedly decreased corticosterone levels in serum of Cln3 Δex7/8 mice with respect to WT animals explains their hyperactivity resulting from reduced stress levels in male and female Cln3 Δex7/8 mice.…”