Exposure to hexanal odor induces extraordinary Fos expression in the medial preoptic area and amygdala of Fyn tyrosine kinase-deficient mice.

Our previous study revealed that the odor of hexanal, which is derived from the wood chips used as bedding, influenced mouse maternal behavior and induced the neonatal death of Fyn-deficient (fyn(-/-)) pups born of fyn(-/-) parents. To clarify what regions of the brain are involved in this effect, we examined which brain regions of fyn(-/-) and Fyn-heterozygous (fyn(+/-)) females were activated by hexanal odor using Fos immunohistochemistry. Hexanal induced Fos immunoreactivity in the primary olfactory cortex and in the medial and central amygdala of both fyn(+/-) and fyn(-/-) mice. In fyn(-/-) females, hexanal also induced the activation of the medial preoptic area and the basolateral and posteriomedial cortical amygdala, which are known to be involved in the control of maternal and emotional behavior.