α1- and β3-Adrenergic Receptor-Mediated Mesolimbic Homeostatic Plasticity Confers Resilience to Social Stress in Susceptible Mice

BACKGROUND: Homeostatic plasticity in mesolimbic dopamine ( DA) neurons plays an essential role in mediating resilience to social stress. Recent evidence implicates an association between stress resilience and projections from the locus coeruleus ( LC) to the ventral tegmental area (VTA) ( LC/VTA) DA system. However, the precise circuitry and molecular mechanisms of the homeostatic plasticity in mesolimbic DA neurons mediated by the LC/VTA circuitry, and its role in conferring resilience to social defeat stress, have not been described. METHODS: In a well-established chronic social defeat stress model of depression, using projection-specific electrophysiological recordings and optogenetic, pharmacological, and molecular profiling techniques, we investigated the functional role and molecular basis of an LC/VTA circuit in conferring resilience to social defeat stress. RESULTS: We found that LC neurons projecting to the VTA exhibit enhanced firing activity in resilient, but not susceptible, mice. Optogenetically mimicking this firing adaptation in susceptible mice reverses their depressionrelated behaviors, and induces reversal of cellular hyperactivity and homeostatic plasticity in VTA DA neurons projecting to the nucleus accumbens. Circuit-specific molecular profiling studies reveal that alpha(1)-and beta(3)-adrenergic receptors are highly expressed in VTA/nucleus accumbens DA neurons. Pharmacologically activating these receptors induces similar proresilient effects at the ion channel and cellular and behavioral levels, whereas antagonizing these receptors blocks the proresilient effect of optogenetic activation of LC/VTA circuit neurons in susceptible mice. CONCLUSIONS: These findings reveal a key role of the LC/VTA circuit in mediating homeostatic plasticity in stress resilience and reveal alpha(1)-and beta(3)-adrenergic receptors as new molecular targets for therapeutically promoting resilience.