High-yawning male rats are more sexually motivated when exposed to sexually receptive female rats in a multichoice sexual paradigm.

During mating, several sensory cues are involved in the sexual interaction process, among which the emission of 50 kHz ultrasonic vocalizations (USVs) plays a key role. We have established two sublines from Sprague-Dawley (SD) rats whose spontaneous yawning frequency differs: high-yawning (HY) with a mean of 20 yawns/h and low-yawning (LY) with a mean of only 2 yawns/h. The HY male rats had more spontaneous penile erections, and when they mated with ovariectomized females primed by sequential administration of estradiol benzoate followed by progesterone for 44 h, HY males had more sexual bouts and longer interintromission intervals that delayed ejaculation during paced mating. During mating, male and female rats emitted 50 kHz ultrasonic vocalizations (USVs), which are a sexual incentive, and these calls promoted sexual interaction. All the tested rats were maintained under standard conditions, and the USVs were recorded with a plug-and-play ultrasound microphone and analyzed using UltraVox XT software. When the rats were evaluated in a four-arm maze paradigm, three arms contained sexually experienced HY, LY or SD males, and the other arm was an empty compartment. Ovariectomized estrous-induced females of each phenotype were introduced and allowed to freely explore the maze for 5 min. All the male groups of rats emitted significantly more USVs when exposed to a receptive female rat than when they were not exposed. Importantly, compared with LY and SD males, HY male had more frequency-modulated and flat calls with shorter latencies, and HY males were significantly preferred by SD and LY estrous-induced females. Overall, HY males had greater sexual motivation associated with a more positive appetitive state.