The odors that newborn rats are exposed to appear to govern the development of synapses that carry information into the rat olfactory cortex, the seat of odor perception, researchers report in Neuron this week.

Kevin Franks and Jeffry Isaacson of the University of California, San Diego, found that in newborn rats, early olfactory experiences caused changes in the relative amounts of two types of glutamate receptors in lateral olfactory tract fibers. Specifically, they observed a decrease in the number of NMDA receptors, which are believed to be important in synaptic plasticity and long-term changes, relative to AMPA receptors, which mediate fast synaptic transmission. The researchers suggest this phenomenon might be associated with "olfactory imprinting," the strong attachment to maternal odors that occurs early in mammalian development.

"The ability of the animal to smell caused downregulation in the number of NMDA receptors," Isaacson told The Scientist. "Very early in...

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