© Springer Science+Business Media, LLC, part of Springer Nature 2018. An important step forward in understanding synaptic transmission has been the discovery that within the realm of G-protein coupled receptors (GPCRs) agonist activation of a receptor type favors physical interactions with different types of neighboring GPCRs. Such receptor interactions lead to receptor oligomerization and formation of receptor heteromers, in which through allosteric mechanisms original protomers change kinetic properties, G-protein recognition and trafficking. Since such changes have important influence on behavior, the aim of this chapter is to describe general strategies to study in the rat the behavioral consequences linked to the formation of molecular heteromers as well as to the application of some commonly used behavioral methods to evaluate the receptor oligomerization on anxious behavior.