Mating reduces the central but not the peripheral stress response in male rats

Abstract

Experimental as well as anecdotal evidence in humans and rodents indicates that sexual activity is not only accompanied by a high level of arousal, but also leads to a number of physiological and behavioural changes. Recently, we could show that mating reduces anxiety-related behaviour in male rats up to 4h after mating. This effect is mediated by central release of the neuropeptide oxytocin (Waldherr&Neumann, 2007). In humans sexual intercourse has been described to reduce the stress reactivity (Brody, 2006) while another recent study describes that mating leads to reduced depressive-like behaviour in male rats (Martinez-Mota et al., 2005). These findings, together with our own results, lead us to the assumption that sexual activity could have a positive effect on the stress responsiveness by influencing central or peripheral parts of the hypothalamo-pituitary-adrenal (HPA) axis. Male Wistar rats with implanted jugular vein catheters were mated with a receptive female for 30min and stressed by one minute of forced swimming either 45 minutes or 4 hours after the termination of the mating period. Blood samples were drawn continuously throughout the procedure to evaluate the peripheral stress response to the sexual interaction by itself as well as to the following stress exposure. The concentrations of ACTH and corticosteron showed significant increases during and shortly after mating. The increase after exposure to the swim stress 45min or 4h after mating however was not changed when compared with non-mated control groups. In a second study, males were submitted to 10min of forced swimming 4h after a 30min mating period. 30min after the termination of the swim stress, animals were killed and their brains processed for evaluation of neuronal activity. In the nucleus paraventricularis of the hypothalamus (PVN), where corticotropin-releasing hormone (CRH) is synthesized, we measured a lack of increase in c-fos mRNA expression following the stress exposure in animals which were mated 4h earlier. In contrast, non-mated control animals showed significant increases in c-fos mRNA expression after the stress exposure.