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Foxes bred for tameness had fewer estrogen-receptor neurons in a hypothalamic region

Research: Behaviour, Anatomy & morphology, Evolution & taxonomy

Silver foxes are a colour form of the Red Fox (Vulpes vulpes). In Russia, foxes have been selectively bred for contrasting social behaviours, including tameness and aggression. The tame line became notably friendlier toward people after only six generations of selection. Researchers asked whether these breeding lines also differed in the cell types found in the hypothalamus, a brain region involved in behaviours including aggression and other social responses.

They examined preserved brains from nine foxes: three bred for tameness, three bred for aggression and three from a wild line. Fluorescent RNA labels helped identify different cell types. The clearest reported difference was in the ventrolateral subdivision of the ventromedial hypothalamus, known as the VMHvl. Tame-bred foxes had fewer neurons expressing estrogen receptors there than aggressive-bred foxes. These receptors allow cells to respond to estrogen.

The cell subtype is of interest because, in mice, activating some estrogen-receptor-expressing neurons in the hypothalamus can trigger attacks. That mouse finding does not establish that the cells have the same role in foxes. The fox study identifies a specific difference in brain-cell composition associated with selection for social behaviour; it does not show whether that difference contributes to tameness or arose alongside it.

Sources and image credit

  1. Hypothalamic cell-type differences associated with selection for tameness in the silver foxPrimary journal source. The abstract supports the reported VMHvl cell-type comparison and finding. Full text and figures were inaccessible for this verification.
  2. From wild to mild: Friendly foxes show changes in brain regionInstitutional account used for the Russian colony context and the preserved-brain and fluorescent-RNA-labeling details.

Image: A silver-coloured red fox (Vulpes vulpes) stands on a wooden platform in an enclosed setting. Photo: Basotxerri / Wikimedia Commons, CC BY-SA 4.0. Representative photograph. · CC BY-SA 4.0 · Source

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