Dopamine D2 receptor signaling on iMSNs is required for initiation and vigor of learned actions

Striatal dopamine D2 receptors (D2Rs) are important for motor output. Selective deletion of D2Rs from indirect pathway-projecting medium spiny neurons (iMSNs) impairs locomotor activities in a task-specific manner. However, the role of D2Rs in the initiation of motor actions in reward seeking and taking is not fully understood, and there is little information about how receptors contribute under different task demands and with different outcome types. The iMSN-D2Rs modulate neuronal activity and synaptic transmission, exerting control on circuit functions that may play distinct roles in action learning and performance. Selective deletion of D2Rs on iMSNs resulted in slower action initiation and response rate in an instrumental conditioning task, but only when performance demand was increased. The iMSN-Drd2KO mice were also slower to initiate swimming in a T-maze procedural learning task but were unimpaired in cognitive function and behavioral flexibility. In contrast, in a Pavlovian discrimination learning task, iMSN-Drd2KO mice exhibited normal acquisition and extinction of rewarded responding. The iMSN-Drd2KO mice showed performance deficits at all phases of rotarod skill learning. These findings reveal that dopamine modulation through iMSN-D2Rs influences the ability to self-initiate actions, as well as the willingness and/or vigor with which these responses are performed. However, these receptors seem to have little influence on simple associative learning or on stimulus-driven responding. The loss of normal D2R roles may contribute to disorders in which impaired dopamine signaling leads to hypokinesia or impaired initiation of specific voluntary actions

Distinct sub-second dopamine signaling in dorsolateral striatum measured by a genetically-encoded fluorescent sensor

The development of genetically encoded dopamine sensors such as dLight has provided a new approach to measuring slow and fast dopamine dynamics both in brain slices and in vivo, possibly enabling dopamine measurements in areas like the dorsolateral striatum (DLS) where previously such recordings with fast-scan cyclic voltammetry (FSCV) were difficult. To test this, we first evaluated dLight photometry in mouse brain slices with simultaneous FSCV and found that both techniques yielded comparable results, but notable differences in responses to dopamine transporter inhibitors, including cocaine. We then used in vivo fiber photometry with dLight in mice to examine responses to cocaine in DLS. We also compared dopamine responses during Pavlovian conditioning across the striatum. We show that dopamine increases were readily detectable in DLS and describe transient dopamine kinetics, as well as slowly developing signals during conditioning. Overall, our findings indicate that dLight photometry is well suited to measuring dopamine dynamics in DLS

Dual Dopaminergic Regulation of Corticostriatal Plasticity by Cholinergic Interneurons and Indirect Pathway Medium Spiny Neurons

Summary: Endocannabinoid (eCB)-mediated long-term depression (LTD) requires dopamine (DA) D2 receptors (D2Rs) for eCB mobilization. The cellular locus of the D2Rs involved in LTD induction remains highly debated. We directly examined the role in LTD induction of D2Rs expressed by striatal cholinergic interneurons (Chls) and indirect pathway medium spiny neurons (iMSNs) using neuron-specific targeted deletion of D2Rs. Deletion of Chl-D2Rs (Chl-Drd2KO) impaired LTD induction in both subtypes of MSNs. LTD induction was restored in the Chl-Drd2KO mice by an M1-selective muscarinic acetylcholine receptor antagonist. In contrast, after the deletion of iMSN-D2Rs (iMSN-Drd2KO), LTD induction was intact in MSNs. Separate interrogation of direct pathway and iMSNs revealed a deficit in LTD induction only at synapses onto iMSNs that lack D2Rs. LTD induction in iMSNs was restored by D2R agonist application. Our findings suggest that Chl D2Rs strongly modulate LTD induction in MSNs, with iMSN-D2Rs having a weaker, iMSN-specific, modulatory effect. : The cellular location of dopamine D2 receptors (D2Rs) involved in corticostriatal long-term synaptic depression (LTD) is controversial. Augustin et al. show that D2Rs on cholinergic interneurons strongly modulate LTD induction at synapses onto all medium spiny neurons (MSNs), while D2Rs on iMSNs weakly modulate induction at synapses onto iMSNs. Keywords: D2 receptors, cholinergic interneurons, iMSNs, dMSNs, long-term depressio

Distinct sub-second dopamine signaling in dorsolateral striatum measured by a genetically-encoded fluorescent sensor.

The development of genetically encoded dopamine sensors such as dLight has provided a new approach to measuring slow and fast dopamine dynamics both in brain slices and in vivo, possibly enabling dopamine measurements in areas like the dorsolateral striatum (DLS) where previously such recordings with fast-scan cyclic voltammetry (FSCV) were difficult. To test this, we first evaluated dLight photometry in mouse brain slices with simultaneous FSCV and found that both techniques yielded comparable results, but notable differences in responses to dopamine transporter inhibitors, including cocaine. We then used in vivo fiber photometry with dLight in mice to examine responses to cocaine in DLS. We also compared dopamine responses during Pavlovian conditioning across the striatum. We show that dopamine increases were readily detectable in DLS and describe transient dopamine kinetics, as well as slowly developing signals during conditioning. Overall, our findings indicate that dLight photometry is well suited to measuring dopamine dynamics in DLS

Chronic Ethanol Consumption Alters Presynaptic Regulation of Dorsal Striatal Dopamine Release in C57BL/6J Mice

Alcohol use disorder (AUD) is characterized by escalating alcohol consumption, preoccupation with alcohol, and continued alcohol consumption despite adverse consequences. Dopamine has been implicated in neural and behavioral processes involved in reward and reinforcement and is a critical neurotransmitter in AUD. Clinical and preclinical research has shown that long-term ethanol exposure can alter dopamine release, though most of this work has focused on nucleus accumbens (NAc). Like the NAc, the dorsal striatum (DS) is implicated in neural and behavioral processes in AUD. However, little work has examined chronic ethanol effects on DS dopamine dynamics. Therefore, we examined the effect of ethanol consumption and withdrawal on dopamine release and its presynaptic regulation with fast-scan cyclic voltammetry in C57BL/6J mice. We found that one month of ethanol consumption did not alter maximal dopamine release or dopamine tissue content. However, we did find that D2 dopamine autoreceptors were sensitized. We also found a decrease in cholinergic control of dopamine release via β2-containing nAChRs on dopamine axons. Interestingly, both effects were reversed following withdrawal, raising the possibility that some of the neuroadaptations in AUD might be reversible in abstinence. Altogether, this work elucidates some of the chronic alcohol-induced neurobiological dysfunctions in the dopamine system

Distinct sub-second dopamine signaling in dorsolateral striatum measured by a genetically-encoded fluorescent sensor

Abstract The development of genetically encoded dopamine sensors such as dLight has provided a new approach to measuring slow and fast dopamine dynamics both in brain slices and in vivo, possibly enabling dopamine measurements in areas like the dorsolateral striatum (DLS) where previously such recordings with fast-scan cyclic voltammetry (FSCV) were difficult. To test this, we first evaluated dLight photometry in mouse brain slices with simultaneous FSCV and found that both techniques yielded comparable results, but notable differences in responses to dopamine transporter inhibitors, including cocaine. We then used in vivo fiber photometry with dLight in mice to examine responses to cocaine in DLS. We also compared dopamine responses during Pavlovian conditioning across the striatum. We show that dopamine increases were readily detectable in DLS and describe transient dopamine kinetics, as well as slowly developing signals during conditioning. Overall, our findings indicate that dLight photometry is well suited to measuring dopamine dynamics in DLS

Sub-second striatal dopamine dynamics assessed by simultaneous fast-scan cyclic voltammetry and fluorescence biosensor

Fast-scan cyclic voltammetry (FSCV) is an electrochemical method used to detect dopamine on a subsecond time scale. Recordings using FSCV in freely behaving animals revolutionized the study of behaviors associated with motivation and learning. Despite this advance, FSCV cannot distinguish between catecholamines, which limits its use to brain regions where dopamine is the predominant neurotransmitter. It has also been difficult to detect dopamine in vivo in some striatal subregions with FSCV. Recently, fluorescent biosensors for dopamine were developed, allowing for discrimination between catecholamines. However, the performance of these biosensors relative to FSCV has not been determined. Thus, we compared fluorescent photometry responses of the dopamine biosensor, dLight, with FSCV. We also used dLight photometry to assess changes in tonic and phasic dopamine, which has not been possible with FSCV. Finally, we examined dopamine dynamics during Pavlovian conditioning in striatal subregions, including the dorsolateral striatum where dopamine measurements are challenging with FSCV

One thousand plant transcriptomes and the phylogenomics of green plants

Abstract: Green plants (Viridiplantae) include around 450,000–500,000 species1, 2 of great diversity and have important roles in terrestrial and aquatic ecosystems. Here, as part of the One Thousand Plant Transcriptomes Initiative, we sequenced the vegetative transcriptomes of 1,124 species that span the diversity of plants in a broad sense (Archaeplastida), including green plants (Viridiplantae), glaucophytes (Glaucophyta) and red algae (Rhodophyta). Our analysis provides a robust phylogenomic framework for examining the evolution of green plants. Most inferred species relationships are well supported across multiple species tree and supermatrix analyses, but discordance among plastid and nuclear gene trees at a few important nodes highlights the complexity of plant genome evolution, including polyploidy, periods of rapid speciation, and extinction. Incomplete sorting of ancestral variation, polyploidization and massive expansions of gene families punctuate the evolutionary history of green plants. Notably, we find that large expansions of gene families preceded the origins of green plants, land plants and vascular plants, whereas whole-genome duplications are inferred to have occurred repeatedly throughout the evolution of flowering plants and ferns. The increasing availability of high-quality plant genome sequences and advances in functional genomics are enabling research on genome evolution across the green tree of life

High-risk exposure without personal protective equipment and infection with SARS-CoV-2 in-hospital workers - The CoV-CONTACT cohort.

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