Brain region specific single-molecule fluorescence imaging.

We developed an approach utilizing nanoscale vesicles extracted from brain regions combined with single molecule imaging to monitor how an animal's physiological condition regulates the dynamics of protein distributions in different brain regions. This method was used to determine the effect of nicotine on the distribution of receptor stoichiometry in different mouse brain regions. Nicotine-induced upregulation of alpha 4 beta 2 nicotinic acetylcholine receptors (nAChRs) is associated with changes in their expression, trafficking, and stoichiometry. The structural assembly of nAChRs has been quantified in cell culture based systems using single molecule techniques. However, these methods are not capable of quantifying biomolecule assembly that takes place in a live animal. Both nicotine-induced upregulation and changes in nAChR stoichiometry differ across brain regions. Our single molecule approach revealed that nicotine acts differentially across brain regions to alter assembly in response to exposure and withdrawal.