Presynaptic Partners of Dorsal Raphe Serotonergic and GABAergic Neurons
ABSTRACT The serotonin system powerfully modulates physiology and behavior in health and disease, yet the circuit mechanisms underlying serotonin neuron activity are poorly understood. The major source of forebrain serotonergic innervation is from the dorsal raphe nucleus (DR), which contains both serotonin and GABA neurons. Using viral tracing combined with electrophysiology, we found that GABA and serotonin neurons in the DR receive excitatory, inhibitory, and peptidergic inputs from the same specific brain regions. Embedded in this overall similarity are important differences. Serotonin neurons are more likely to receive synaptic inputs from anterior neocortex while GABA neurons receive disproportionally higher input from the central amygdala. Local input mapping revealed extensive serotonin-serotonin as well as GABA-serotonin connectivity with a distinct spatial organization. Covariance analysis suggests heterogeneity of both serotonin and GABA neurons with respect to the inputs they receive. These analyses provide a foundation for further functional dissection of the serotonin system.
- SourceAvailable from: Jingfeng Zhou
[Show abstract] [Hide abstract]
- "Recent transsynaptic tracings reveal that DRN GABA neurons share a largely similar input pattern with 5-HT neurons (Dorocic et al. 2014; Weissbourd et al. 2014). However, neurons from the central amygdala and the bed nucleus of the stria terminalis preferentially innervate GABAergic neurons, suggesting that these brain areas exert a more powerful modulation of DRN functions through GABAergic interneurons (Weissbourd et al. 2014). A small fraction of DRN neurons (1000 in mice) in the rostral-dorsal part of the DRN expresses the dopamine markers tyrosine hydroxylase and dopamine transporter (DAT) (Flores et al. 2004). "
ABSTRACT: The dorsal raphe nucleus (DRN) represents one of the most sensitive reward sites in the brain. However, the exact relationship between DRN neuronal activity and reward signaling has been elusive. In this review, we will summarize anatomical, pharmacological, optogenetics, and electrophysiological studies on the functions and circuit mechanisms of DRN neurons in reward processing. The DRN is commonly associated with serotonin (5-hydroxytryptamine; 5-HT), but this nucleus also contains neurons of the neurotransmitter phenotypes of glutamate, GABA and dopamine. Pharmacological studies indicate that 5-HT might be involved in modulating reward- or punishment-related behaviors. Recent optogenetic stimulations demonstrate that transient activation of DRN neurons produces strong reinforcement signals that are carried out primarily by glutamate. Moreover, activation of DRN 5-HT neurons enhances reward waiting. Electrophysiological recordings reveal that the activity of DRN neurons exhibits diverse behavioral correlates in reward-related tasks. Studies so far thus demonstrate the strong power of DRN neurons in reward signaling and at the same time invite additional efforts to dissect the roles and mechanisms of different DRN neuron types in various processes of reward-related behaviors. © 2015 Luo et al.; Published by Cold Spring Harbor Laboratory Press.Learning & memory (Cold Spring Harbor, N.Y.) 09/2015; 22(9):452-60. DOI:10.1101/lm.037317.114 · 4.38 Impact Factor
[Show abstract] [Hide abstract]
- "rong et al . , 1983 ) , dopaminergic ( Björklund and Dunnett , 2007 ) and serotonergic neurons ( Fu et al . , 2010 ; Russo and Nestler , 2013 ) , have been analyzed using traditional methods ; however , these studies were limited primarily to local areas . Recently , the projection , location and distribution of specific subtypes of interneurons ( Weissbourd et al . , 2014 ) and of serotonergic neurons ( Pollak Dorocic et al . , 2014 ) have been characterized in the mouse brain with manually sectioning and imaging ."
ABSTRACT: There are some unsolvable fundamental questions, such as cell type classification, neural circuit tracing and neurovascular coupling, though great progresses are being made in neuroscience. Because of the structural features of neurons and neural circuits, the solution of these questions needs us to break through the current technology of neuroanatomy for acquiring the exactly fine morphology of neuron and vessels and tracing long-distant circuit at axonal resolution in the whole brain of mammals. Combined with fast-developing labeling techniques, efficient whole-brain optical imaging technology emerging at the right moment presents a huge potential in the structure and function research of specific-function neuron and neural circuit. In this review, we summarize brain-wide optical tomography techniques, review the progress on visible brain neuronal/vascular networks benefit from these novel techniques, and prospect the future technical development.Frontiers in Neuroanatomy 05/2015; 9. DOI:10.3389/fnana.2015.00070 · 4.18 Impact Factor
- "d the same inputs , in largely the same proportions , with a few unique exceptions that include the motor cortices and subthalamic nucleus for the SNc and the lateral hypothalamus for the VTA . A similar approach has been used to examine the inputs to different groups of serotonergic neurons ( Ogawa et al . , 2014 ; Pollak Dorocic et al . , 2014 ; Weissbourd et al . , 2014 ) , as well as the dorsal striatum ( Wall et al . , 2013 ) and hippocampus ( Sun et al . , 2014 ) ."
Article: Neuroanatomy goes viral![Show abstract] [Hide abstract]
ABSTRACT: The nervous system is complex not simply because of the enormous number of neurons it contains but by virtue of the specificity with which they are connected. Unraveling this specificity is the task of neuroanatomy. In this endeavor, neuroanatomists have traditionally exploited an impressive array of tools ranging from the Golgi method to electron microscopy. An ideal method for studying anatomy would label neurons that are interconnected, and, in addition, allow expression of foreign genes in these neurons. Fortuitously, nature has already partially developed such a method in the form of neurotropic viruses, which have evolved to deliver their genetic material between synaptically connected neurons while largely eluding glia and the immune system. While these characteristics make some of these viruses a threat to human health, simple modifications allow them to be used in controlled experimental settings, thus enabling neuroanatomists to trace multi-synaptic connections within and across brain regions. Wild-type neurotropic viruses, such as rabies and alpha-herpes virus, have already contributed greatly to our understanding of brain connectivity, and modern molecular techniques have enabled the construction of recombinant forms of these and other viruses. These newly engineered reagents are particularly useful, as they can target genetically defined populations of neurons, spread only one synapse to either inputs or outputs, and carry instructions by which the targeted neurons can be made to express exogenous proteins, such as calcium sensors or light-sensitive ion channels, that can be used to study neuronal function. In this review, we address these uniquely powerful features of the viruses already in the neuroanatomist's toolbox, as well as the aspects of their biology that currently limit their utility. Based on the latter, we consider strategies for improving viral tracing methods by reducing toxicity, improving control of transsynaptic spread, and extending tFrontiers in Neuroanatomy 05/2015; 9:80. DOI:10.3389/fnana.2015.00080 · 4.18 Impact Factor