Priming Effects of Female Pheromones on Reproductive Physiology in Gαo Knockout Male Mice
Primer effects are a type of communication, where pheromones affect the bodily functions of other individuals. Primer effects provide benefits for reproduction, as animals can prepare their bodies for mating successfully. For male mice, reproductive changes can take place when exposed to soiled female bedding containing female pheromones. These pheromones are detected by the vomeronasal organ (VNO), located within the nasal cavity. The VNO contains two neuron types, expressing either Gαi2 or Gαo G-proteins. By knocking-out Gαo neurons it is possible to determine whether these neurons are important in male mice to regulate responses to female pheromones. In this project, I observed that neurons within the VNO showed a large increase in activation after 1hr of female bedding exposure, irrespective of whether Gαo was deleted in the VNO. When mice were given chronic long-term bedding exposure over 10 weeks, then female bedding exposure, this resulted in fewer neurons being activated in the vomeronasal organ, compared to those without long-term bedding exposure, suggesting desensitization of the response. I observed no effect of long-term bedding exposure on sperm motility or testicular counts in either genotype, although deletion of Gαo in the VNO unexpectedly increased epididymal sperm counts. Over the ten-week experiment mice with Gαo deleted also lost more weight compared to wildtype mice. A decrease in body weight could suggest reproductive investment, as energy is being investing in sperm production and secreting pheromones to attract female mice. My results are partially inconsistent with previous studies because I did not observe primer effects on male reproductive physiology with long-term female bedding exposure in either genotype. Surprisingly I found evidence of greater reproductive investment in mice that do not express Gαo in the VNO. I hypothesize that this may be because they have not perceived male pheromones when caged with other males prior to the experiment. Male-male pheromonal communication suppresses reproductive function, and thus deletion of Gαo may inhibit these negative effects from occurring.
Advisor: Garratt, Micheal
Degree Name: Bachelor of Biomedical Sciences with Honours
Degree Discipline: Anatomy
Publisher: University of Otago
Keywords: Pheromones; Vomeronasal Organ; Primer Effects
Research Type: Thesis