Monday, September 10, 2007

The smell of an alpha male....

Pheromones influence sexual behavior and reproduction in rodents. Mak et al report that:
...the pheromones of dominant (but not subordinate) males stimulate neuronal production in both the olfactory bulb and hippocampus of female mice, which are independently mediated by prolactin and luteinizing hormone, respectively. Neurogenesis induced by dominant-male pheromones correlates with a female preference for dominant males over subordinate males, whereas blocking neurogenesis with the mitotic inhibitor cytosine arabinoside eliminated this preference. These results suggest that male pheromones are involved in regulating neurogenesis in both the olfactory bulb and hippocampus, which may be important for female reproductive success.
I keep wondering if we won't be finding evidence for a version of this effect (perhaps more subtle) in humans... would the cheerleader, like the female rat in the box below, be more likely to hang out with the star quarterback if she had smelled his sweaty jersey a day earlier??

An illustration from the summary review by DiRocco and Xia:
Figure legend: Dominant male pheromones stimulate neurogenesis in females.
(a) Female mice exposed to dominant male pheromones spent more time sniffing the dominant male, whereas females exposed to subordinate male pheromones did not show any preference. (b) Exposing female mice to pheromones from dominant males led to increased neurogenesis in the subventricular zone (SVZ) and dentate gyrus (DG). Pheromones signal the main olfactory epithelium (MOE)–main olfactory bulb (MOB) axis, which relays the signal to the hypothalamus (HYP)–pituitary (PIT) axis, leading to the release of luteinizing hormone (LH) and prolactin (PRL). LH appeared to stimulate neurogenesis in the dentate gyrus of the hippocampus, whereas prolactin induced neurogenesis in the SVZ and MOB. It is hypothesized that pheromone-induced neurogenesis may underlie female mating preference for the dominant male. NC, nasal cavity; RMS, rostral migratory stream; green circles, newborn neurons.

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