The Nature articles on the role of dopamine and depression add greatly to our understanding of this transmitter system in affective disorders. While on the surface such studies may be viewed as being opposite in nature, both are highly consistent with results from our lab and others. We (Valenti et al., 2011) and others have shown that strong, acute stressors can activate dopamine neuron activity; however, when measured after long bouts of inescapable stress or following an incubation period, the activity of these neurons is markedly depressed (Moore et al., 2001; Valenti et al., 2012; Chang and Grace, 2013). These studies suggest that dopamine system activation during the stressor may be a precedent for dopamine system downregulation following termination of the stressor. Indeed, in the uncontrollable chronic stress model and in the learned helplessness model of depression (Chang and Grace, 2012; Belujon et al., 2012), we have found that...  Read more

The Nature articles on the role of dopamine and depression add greatly to our understanding of this transmitter system in affective disorders. While on the surface such studies may be viewed as being opposite in nature, both are highly consistent with results from our lab and others. We (Valenti et al., 2011) and others have shown that strong, acute stressors can activate dopamine neuron activity; however, when measured after long bouts of inescapable stress or following an incubation period, the activity of these neurons is markedly depressed (Moore et al., 2001; Valenti et al., 2012; Chang and Grace, 2013). These studies suggest that dopamine system activation during the stressor may be a precedent for dopamine system downregulation following termination of the stressor. Indeed, in the uncontrollable chronic stress model and in the learned helplessness model of depression (Chang and Grace, 2012; Belujon et al., 2012), we have found that dopamine neuron population activity depression correlates with behavioral indices of depressive-like behavior in rats.

The data from the Han and Deisseroth laboratories are actually highly consistent with these data. Thus, Han showed that phasic activation of dopamine neurons potentiates the effects of stress on subsequent depression (consistent with our studies showing dopamine activation during the initial stress events), whereas restoring dopamine activity during the depressed condition in Deisseroth's paper relieves the symptoms due to dopamine system downregulation.

Therefore, in our opinion, each phase of the depression process may have a dopamine component: an activation during the induction phase and an attenuation during symptom expression. Taken together, these findings provide unique insights into the process and expression of depression.

References:

Belujon, P., Dollish, H.D. and Grace, A.A. (2012) Ketamine restores activity of the dopamine system selectively in rats exhibiting learned helplessness in an animal model of depression. Program No. 774.02.2012. Neuroscience Meeting Planner, New Orleans, LA. Society for Neuroscience, 2012. Online.

Chang, C.H. and Grace, A.A. (2012) Chronic mild stress induces anxiety-like behavior and down-regulation of dopamine system activity in rats. Program No. 774.13.2012. Neuroscience Meeting Planner, New Orleans, LA. Society for Neuroscience, 2012. Online.

Chang, C.-H. and Grace, A.A. (2013) Amygdala beta noradrenergic receptors modulate delayed down-regulation of dopamine activity following restraint. Journal of Neuroscience (in press).

Moore, H., Rose, H.J.. and Grace, A.A. (2001) Chronic cold stress reduces the spontaneous activity of ventral tegmental dopamine neurons. Neuropsychopharmacology 24: 410-419. Abstract

Valenti, O., Lodge, D.J. and Grace, A.A. (2011) Aversive stimuli alter ventral tegmental area dopamine neuron activity via a common action in the ventral hippocampus. Journal of Neuroscience 31: 4280-4289. Abstract

Valenti, O., Gill, K.M. and Grace, A.A. (2012) Different stressors produce excitation or inhibition of mesolimbic dopamine neuron activity: Response alteration by stress pre-exposure. European Journal of Neuroscience 35: 1312-1321. Abstract