Depression Treatment: Rapid Regulation of Depression-Related Behaviours by Control of Midbrain Dopamine Neurons.

Rapid regulation of depression-related behaviours by control of midbrain dopamine neurons.

Filed under: Depression Treatment

Nature. 2012 Dec 12;
Chaudhury D, Walsh JJ, Friedman AK, Juarez B, Ku SM, Koo JW, Ferguson D, Tsai HC, Pomeranz L, Christoffel DJ, Nectow AR, Ekstrand M, Domingos A, Mazei-Robison MS, Mouzon E, Lobo MK, Neve RL, Friedman JM, Russo SJ, Deisseroth K, Nestler EJ, Han MH

Ventral tegmental area (VTA) dopamine neurons in the brain’s reward circuit have a crucial role in mediating stress responses, including determining susceptibility versus resilience to social-stress-induced behavioural abnormalities. VTA dopamine neurons show two in vivo patterns of firing: low frequency tonic firing and high frequency phasic firing. Phasic firing of the neurons, which is well known to encode reward signals, is upregulated by repeated social-defeat stress, a highly validated mouse model of depression. Surprisingly, this pathophysiological effect is seen in susceptible mice only, with no apparent change in firing rate in resilient individuals. However, direct evidence-in real time-linking dopamine neuron phasic firing in promoting the susceptible (depression-like) phenotype is lacking. Here we took advantage of the temporal precision and cell-type and projection-pathway specificity of optogenetics to show that enhanced phasic firing of these neurons mediates susceptibility to social-defeat stress in freely behaving mice. We show that optogenetic induction of phasic, but not tonic, firing in VTA dopamine neurons of mice undergoing a subthreshold social-defeat paradigm rapidly induced a susceptible phenotype as measured by social avoidance and decreased sucrose preference. Optogenetic phasic stimulation of these neurons also quickly induced a susceptible phenotype in previously resilient mice that had been subjected to repeated social-defeat stress. Furthermore, we show differences in projection-pathway specificity in promoting stress susceptibility: phasic activation of VTA neurons projecting to the nucleus accumbens (NAc), but not to the medial prefrontal cortex (mPFC), induced susceptibility to social-defeat stress. Conversely, optogenetic inhibition of the VTA-NAc projection induced resilience, whereas inhibition of the VTA-mPFC projection promoted susceptibility. Overall, these studies reveal novel firing-pattern- and neural-circuit-specific mechanisms of depression.
HubMed – depression

 

Dopamine neurons modulate neural encoding and expression of depression-related behaviour.

Filed under: Depression Treatment

Nature. 2012 Dec 12;
Tye KM, Mirzabekov JJ, Warden MR, Ferenczi EA, Tsai HC, Finkelstein J, Kim SY, Adhikari A, Thompson KR, Andalman AS, Gunaydin LA, Witten IB, Deisseroth K

Major depression is characterized by diverse debilitating symptoms that include hopelessness and anhedonia. Dopamine neurons involved in reward and motivation are among many neural populations that have been hypothesized to be relevant, and certain antidepressant treatments, including medications and brain stimulation therapies, can influence the complex dopamine system. Until now it has not been possible to test this hypothesis directly, even in animal models, as existing therapeutic interventions are unable to specifically target dopamine neurons. Here we investigated directly the causal contributions of defined dopamine neurons to multidimensional depression-like phenotypes induced by chronic mild stress, by integrating behavioural, pharmacological, optogenetic and electrophysiological methods in freely moving rodents. We found that bidirectional control (inhibition or excitation) of specified midbrain dopamine neurons immediately and bidirectionally modulates (induces or relieves) multiple independent depression symptoms caused by chronic stress. By probing the circuit implementation of these effects, we observed that optogenetic recruitment of these dopamine neurons potently alters the neural encoding of depression-related behaviours in the downstream nucleus accumbens of freely moving rodents, suggesting that processes affecting depression symptoms may involve alterations in the neural encoding of action in limbic circuitry.
HubMed – depression

 

The genetic rescue of two bottlenecked South Island robin populations using translocations of inbred donors.

Filed under: Depression Treatment

Proc Biol Sci. 2013; 280(1752): 20122228
Heber S, Varsani A, Kuhn S, Girg A, Kempenaers B, Briskie J

Populations forced through bottlenecks typically lose genetic variation and exhibit inbreeding depression. ‘Genetic rescue’ techniques that introduce individuals from outbred populations can be highly effective in reversing the deleterious effects of inbreeding, but have limited application for the majority of endangered species, which survive only in a few bottlenecked populations. We tested the effectiveness of using highly inbred populations as donors to rescue two isolated and bottlenecked populations of the South Island robin (Petroica australis). Reciprocal translocations significantly increased heterozygosity and allelic diversity. Increased genetic diversity was accompanied by increased juvenile survival and recruitment, sperm quality, and immunocompetence of hybrid individuals (crosses between the two populations) compared with inbred control individuals (crosses within each population). Our results confirm that the implementation of ‘genetic rescue’ using bottlenecked populations as donors provides a way of preserving endangered species and restoring their viability when outbred donor populations no longer exist.
HubMed – depression

 

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