The formation of new inhibitory synapses is essential to counterbalance a strong excitatory activity and maintain dendritic coordination between excitation and inhibition. We recently demonstrated that the activation of excitatory spines is followed by the production of endocannabinoids in dendrites, which mediates the formation of new inhibitory boutons via axonal CB1 receptors. Bouton formation was found to depend on an increase of the second messenger cyclic adenosine monophosphate (cAMP) and the activation of the downstream protein kinase A (PKA). We ask whether other neuromodulators are also involved in the formation of inhibitory boutons through the regulation of cAMP/PKA signaling. In CA1 region of mouse hippocampal organotypic brain slices, we monitored the formation of individual inhibitory boutons using two-photon (2p) microscopy. We found that a brief application of dopamine D1 receptor agonist increased the number of newly formed inhibitory boutons in axons, while the application of norepinephrine did not affect the formation of inhibitory boutons. In parallel, we characterized the cAMP/PKA dynamics in inhibitory neurons using novel biosensors developed for 2p fluorescence (lifetime) imaging. While dopamine D1 receptor agonist only increased PKA activity in a fraction of inhibitory neurons, norepinephrine produced a strong increase of PKA activity in all hippocampal inhibitory neurons. Importantly, we have indications that PKA signaling is differentially regulated in subcellular compartments. Our results suggest that the promotion of inhibitory bouton formation by cAMP/PKA activation could be a general effect of neuromodulators. We are currently investigating the differential regulation of cAMP/PKA dynamics in axons and dendrites.