Selective activation of the A10, but not A9, dopamine neurons in the rat by the predator odor, 2,5-dihydro-2,4,5-trimethylthiazoline.

2,5-Dihydro-2,4,5-trimethylthiazoline (TMT), a predator odor, has many similar attributes to classic stresses, including activation of cortical dopamine (DA) turnover. Here, we report that exposure to TMT resulted in the expression of c-fos, an immediate-early gene, in A10, but not A9, DA neurons using immunocytochemical techniques. The magnitude of TMT-associated Fos expression was less than that seen with intermittent, mild footshock. Exposure to the control odor, butyric acid, did not result in the increase of expression of Fos protein. Fos is thought to be involved with long-term changes in a neuron's structure and function that may underlie learning by altering the expression of other genes with AP-1 sites. Exposure to TMT may result in alterations in the A10 neurons that could contribute to an altered response to subsequent stresses.