Monday, November 13, 2017

Male prairie voles enjoy forcing sex on the females, the females do not enjoy not being able to escape

Mating and social exposure induces an opioid-dependent conditioned place preference in male but not in female prairie voles (Microtus ochrogaster). M. Ulloa et al. Hormones and Behavior, Volume 97, January 2018, Pages 47–55.

•    In male prairie voles (M. ochrogaster), one ejaculation is rewarding.
•    In males, social cohabitation with mating for 6 h that leads to pair bonding is rewarding.
•    In females, neither condition induces conditioned place preference.
•    The reward state induced by one ejaculation or 6 h of mating is opioid dependent.

Abstract: In rodents, sexual stimulation induces a positive affective state that is evaluated by the conditioned place preference (CPP) test. Opioids are released during sexual behavior and modulate the rewarding properties of this behavior. Prairie voles (Microtus ochrogaster) are a socially monogamous species, in which copulation with cohabitation for 6 h induces a pair bond. However, the mating-induced reward state that could contribute to the establishment of the long-term pair bond has not been evaluated in this species. The present study aimed to determine whether one ejaculation or cohabitation with mating for 6 h is rewarding for voles. We also evaluated whether this state is opioid dependent. Our results demonstrate that mating with one ejaculation and social cohabitation with mating for 6 h induce a CPP in males, while exposure to a sexually receptive female without mating did not induce CPP. In the female vole, mating until one ejaculation, social cohabitation with mating, or exposure to a male without physical interaction for 6 h did not induce CPP. To evaluate whether the rewarding state in males is opioid dependent, the antagonist naloxone was injected i.p. The administration of naloxone blocked the rewarding state induced by one ejaculation and by social cohabitation with mating. Our results demonstrate that in the prairie vole, on the basis of the CPP in the testing conditions used here, the stimulation received with one ejaculation and the mating conditions that lead to pair bonding formation may be rewarding for males, and this reward state is opioid dependent.

Keywords: Sexual reward; Conditioned place preference; Social cohabitation with mating; Opioids and voles

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