Central administration of oxytocin differentially increases yawning, penile erections and scratching in high- (HY) and low-yawning (LY) sublines of Sprague-Dawley rats.

Central administration of oxytocin has been shown to induce yawning, penile erection, grooming and scratching. Yawning and penile erections are due to activation of oxytocinergic neurons in the paraventricular nucleus of the hypothalamus. We selectively bred two sublines from Sprague-Dawley rats, one with a high-yawning frequency (HY) of 20yawns/h, and one with a low-yawning (LY) frequency of 2yawns/h. The aim of the current study was to analyze the behavioral effects of centrally-administered oxytocin [15ng-10μg; intracerebroventricularly (i.c.v.)] on yawning, penile erections, grooming and scratching in adult male rats from both sublines. Oxytocin produced a dose-dependent increase in yawning and penile erection frequencies and this effect was significantly higher in the HY, compared to the LY, subline. However, the number of oxytocin-induced scratching bouts was significantly higher in the LY, compared to the HY group. In conclusion, these sublines represent a suitable model for detailed analysis of behavior induced by oxytocin and other neuropeptides in animals with different spontaneous expression of behavioral traits.