Association between estrus cycle-related aggression and tidal volume variability in female Wistar rats

Premenstrual dysphoria is characterized by symptoms such as irritability and depressed mood, present during the luteal phase of the menstrual cycle, and disappearing shortly after the onset of menstruation. Subjects with premenstrual dysphoria have previously been reported to display enhanced respiratory variability, and to experience anxiety when exposed to panicogens, such as CO2. In the present study, the possible influence of the estrus cycle and estrus cycle-related aggression on respiratory variability was investigated in female rats of the Wistar strain. The rats were subdivided into two groups: those displaying estrus cycle-related aggression, as evaluated using the resident intruder paradigm, and those not showing aggression throughout the estrus cycle. This model has been developed to serve as an animal model of premenstrual irritability. The former group was found to display higher tidal volume variability in diestrus, as compared to the non-aggressive rats. There was no effect of estrus cycle phase on respiratory variability. These results are well in line with the clinical observation that women with premenstrual dysphoria display higher respiratory variability than controls, and the notion that respiratory variability is a parameter of interest in this context. In our opinion, they also strengthen the concept of this animal model as a model of premenstrual irritability.