Reduced Lordosis and Enhanced Aggression in Paced and Non-Paced Mating in Diabetic Female Rats

Abstract

Background Clinical studies have shown altered sexual function in people with diabetes; basic science studies, using the streptozotocin (STZ)-induced animal model of type 1 diabetes mellitus (DM1), have consistently reported decreased sexual behavior in hyperglycemic female animals, but features of sexual motivation and aggressive behavior have not been explored in these animals. Aim To study several parameters that denote sexual motivation in STZ-treated female rats and to compare behavioral features of sexual behavior and aggression in non-paced mating (NPM) and paced mating (PM) conditions. Methods DM1 was induced by injecting STZ (diluted in citrate buffer) at a dose of 50 mg/kg intraperitoneally over 2 consecutive days into ovariectomized Wistar rats. 10 days later, female rats were treated with estradiol benzoate (10 μg, -24 hours) and progesterone (3 mg, -4 hours); their sexual behavior (including lordosis quotient, lordosis intensity, and proceptivity) and aggression were evaluated under NPM and PM conditions. Body weight, blood glucose levels, and spontaneous ambulatory activity also were measured. A group of STZ-treated animals was administered a long-acting insulin analogue (glargine) every 12 hours for 8 days, and their sexual and aggressive behaviors were evaluated in NPM. Outcomes We quantified body weight, blood glucose level, spontaneous ambulatory activity, and sexual and aggressive behaviors in NPM and PM; the time the female rats spent interacting with the male rat or in the male rat's chamber also was registered in PM. Results Compared with controls, STZ-treated ovariectomized rats lost body weight, had increased blood glucose levels, and had unchanged spontaneous ambulatory activity. In the PM and NPM conditions, animals showed decreased lordosis quotient and lordosis intensity, increased aggression, and unaltered proceptivity, although in NPM the effects of STZ treatment on aggression were more drastic and were completely prevented by insulin. In PM no differences were found between diabetic and control female rats in the time interacting with the male rat or in the male rat's chamber. Clinical Translation These findings support the observation of increased prevalence of sexual dysfunctions and aggression in the clinical setting of DM1. Strengths and Limitations The main strength of this study is that it analyzed sexual behavior under PM and NPM conditions and aggression in STZ-treated female rats. Its main limitations are that the model of DM1 represents only 10% of the affected population and that no specific treatment is proposed for the sexual dysfunctions. Conclusion These results suggest that STZ-treated rats have decreased sexual receptivity in NPM and PM, accompanied by increased aggressiveness in NPM.

Diabetic female rats exhibit defensive aggression during mating

“…To the best of our knowledge, in females there is only a single work reporting increased aggressiveness in STZ-treated rats tested in two distinct mating conditions (Hernandez-Munive, Rebolledo-Solleiro, Ventura-Aquino, & Fernandez-Guasti, 2018). In that study, we showed that in the non-paced mating paradigm (NPM), which implies that the timing of copulation is imposed by the male (resulting in some rejection behaviors by the females) (Hardy & DeBold, 1972), the hyperglycemic females displayed high levels of aggression, which were diminished after insulin administration (Hernandez-Munive et al, 2018).…”

“…To the best of our knowledge, in females there is only a single work reporting increased aggressiveness in STZ-treated rats tested in two distinct mating conditions (Hernandez-Munive, Rebolledo-Solleiro, Ventura-Aquino, & Fernandez-Guasti, 2018). In that study, we showed that in the non-paced mating paradigm (NPM), which implies that the timing of copulation is imposed by the male (resulting in some rejection behaviors by the females) (Hardy & DeBold, 1972), the hyperglycemic females displayed high levels of aggression, which were diminished after insulin administration (Hernandez-Munive et al, 2018). When evaluated in the paced mating paradigm (PM), where the number of aggressive behaviors in control animals is minimal because the female controls the timing of copulation by moving away from the male (Paredes & Vazquez, 1999), the aggressiveness of hyperglycemic females also tended to increase (Hernandez-Munive et al, 2018).…”

“…In that study, we showed that in the non-paced mating paradigm (NPM), which implies that the timing of copulation is imposed by the male (resulting in some rejection behaviors by the females) (Hardy & DeBold, 1972), the hyperglycemic females displayed high levels of aggression, which were diminished after insulin administration (Hernandez-Munive et al, 2018). When evaluated in the paced mating paradigm (PM), where the number of aggressive behaviors in control animals is minimal because the female controls the timing of copulation by moving away from the male (Paredes & Vazquez, 1999), the aggressiveness of hyperglycemic females also tended to increase (Hernandez-Munive et al, 2018). In that report, however, we failed to analyze the features of the aggressive behaviors.…”