Recent preclinical and clinical observations identified alterations in the midbrain along the prodromal phase of Alzheimer’s disease (AD). These alterations include degeneration of monoamine neurons, resulting in deficits in ascending monoaminergic pathways in target areas related to AD, as the hippocampus. Incidentally, recent findings link the role of monoamines in the modulation of neuroinflammation.Here we sought to prove how the degeneration of the midbrain, leading to monoamine loss in the hippocampus, activates a neuroinflammatory response, in addition to alterations of synaptic plasticity and monoamine-associated behavior.To do this, we generated two different models of midbrain lesion in young wild-type (C57BL/6N) mice. To perturb simultaneously the dopaminergic and serotonergic systems, we infused in the midbrain a combination of two adeno-associated viruses to overexpress the Caspase-3 under the Tyrosine-Hydroxylase promoter, expressed in dopaminergic midbrain neurons and, ectopically, in neighboring serotonergic cells of the interpeduncular nucleus. To perturb dopamine release alone, we infused the 6-hydroxydopamine toxin in the midbrain.Both lesions reduced the hippocampal monoamine levels and impaired synaptic plasticity and memory function. Interestingly, only the combined loss of dopamine and serotonin induced hippocampal neuroinflammation, characterized by microglia reactivity and interleukin-1β release mediated by NLRP3-inflammasome activation. Intriguingly, pharmacological treatments aimed at boosting dopamine or serotonin signaling blunted hippocampal NLRP3-mediated neuroinflammation.Overall, our results demonstrate that the neuroinflammatory events precociously observed in AD could be a direct consequence of an early midbrain alteration and prove an important role of midbrain monoamines as negative regulators of neuroinflammation, with relevant implications for neurodegenerative diseases.