LEAVING the safety of mother鈥檚 care and learning to make your own way are key to growing up. How rat pups make this transition is now becoming clearer.
A team led by Regina Sullivan of New York University鈥檚 Langone Medical Center previously found that young pups are attracted to odours even when those smells are paired with electric shocks. Only at about 10 days old do pups learn to link odours to negative stimuli. Sullivan also found that odours associated with mother initially suppress the release of the stress hormone corticosterone in pups.
Now her team has shown that this suppression reduces levels of the neurotransmitter dopamine in the amygdala, the brain鈥檚 鈥渇ear centre鈥�. Dopamine-linked genes, which were relatively inactive in 8-day-old rat pups exposed to shock-paired odours, became more active when the pups were given corticosterone. These pups also learned to avoid the odours (Nature Neuroscience, ).
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Rats are born helpless, so their initial maternal attachment is vital, but later, learning about danger is important. If similar mechanisms operate in the brains of human infants, it may help explain why they remain strongly attached even to abusive mothers.