See Borgkvist et al. (doi:) for a scientific commentary on this article.D2 autoreceptors and L-type calcium channels are both implicated in Parkinson’s disease, but how they interact is unclear. Dragicevic et al. reveal that L-type calcium channels can modulate D2-autoreceptor responses via the neuronal calcium sensor NCS-1. This dopamine-dependent signalling network is altered in Parkinson’s disease and could represent a therapeutic target.

Degeneration of dopaminergic neurons in the substantia nigra causes the motor symptoms of Parkinson’s disease. The mechanisms underlying this age-dependent and region-selective neurodegeneration remain unclear. Here we identify Cav2.3 channels as regulators of nigral neuronal viability. Cav2.3 transcripts were more abundant than other voltage-gated Ca2+ channels in mouse nigral neurons and upregulated during aging. Plasmalemmal Cav2.3 protein was higher than in dopaminergic neurons of the ventral tegmental area, which do not degenerate in Parkinson’s disease. Cav2.3 knockout reduced activity-associated nigral somatic Ca2+ signals and Ca2+-dependent after-hyperpolarizations, and afforded full protection from degeneration in vivo in a neurotoxin Parkinson’s mouse model. Cav2.3 deficiency upregulated transcripts for NCS-1, a Ca2+-binding protein implicated in neuroprotection. Conversely, NCS-1 knockout exacerbated nigral neurodegeneration and downregulated Cav2.3. Moreover, NCS-1 levels were reduced in a human iPSC-model of familial Parkinson’s. Thus, Cav2.3 and NCS-1 may constitute potential therapeutic targets for combatting Ca2+-dependent neurodegeneration in Parkinson’s disease.

There is strong evidence that the core deficits of schizophrenia result from dysfunction of the dopamine (DA) system, but details of this dysfunction remain unclear. We previously reported a model of transgenic mice that selectively and reversibly overexpress DA D2 receptors (D2Rs) in the striatum (D2R-OE mice). D2R-OE mice display deficits in cognition and motivation that are strikingly similar to the deficits in cognition and motivation observed in patients with schizophrenia. Here, we show that in vivo, both the firing rate (tonic activity) and burst firing (phasic activity) of identified midbrain DA neurons are impaired in the ventral tegmental area (VTA), but not in the substantia nigra (SN), of D2R-OE mice. Normalizing striatal D2R activity by switching off the transgene in adulthood recovered the reduction in tonic activity of VTA DA neurons, which is concordant with the rescue in motivation that we previously reported in our model. On the other hand, the reduction in burst activity was not rescued, which may be reflected in the observed persistence of cognitive deficits in D2R-OE mice. We have identified a potential molecular mechanism for the altered activity of DA VTA neurons in D2R-OE mice: a reduction in the expression of distinct NMDA receptor subunits selectively in identified mesolimbic DA VTA, but not nigrostriatal DA SN, neurons. These results suggest that functional deficits relevant for schizophrenia symptoms may involve differential regulation of selective DA pathways.ventral tegmental area | dopamine D2 receptor | burst activity | NMDA receptor | schizophrenia D eficits in cognition and motivation are core features of schizophrenia (1, 2). These symptoms are listed in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition as a diagnostic criterion for schizophrenia spectrum disorder (3) and have a significant impact on patients' overall functioning and quality of life (4, 5). Currently, there are no effective treatments for these disabling aspects of the disease. Therefore, a high priority in the study of schizophrenia is to increase our understanding of the neurobiology of cognitive and motivational deficits. The midbrain dopamine (DA) system affects cognition and motivation in healthy subjects. It includes DA neurons of the ventral tegmental area (VTA), projecting to prefrontal cortex (PFC) and limbic areas (e.g., ventral striatum), and DA neurons of the substantia nigra (SN), projecting to the dorsal striatum (6). Involvement of the midbrain DA system is strongly implicated in both the cognitive and motivational deficits observed in schizophrenia (7,8). Moreover, it is well documented that the DA system is altered in patients with schizophrenia (reviewed in refs. 9, 10).To model the increase in striatal DA D2 receptor (D2R) activity observed in patients with schizophrenia, we previously generated transgenic mice that selectively and reversibly overexpress D2Rs in the striatum (D2R-OE mice) (11). In this model, expression of the transgenic D2Rs is restricted to the postsy...