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Steinbusch HWM, Dolatkhah MA, Hopkins DA. Anatomical and neurochemical organization of the serotonergic system in the mammalian brain and in particular the involvement of the dorsal raphe nucleus in relation to neurological diseases. PROGRESS IN BRAIN RESEARCH 2021; 261:41-81. [PMID: 33785137 DOI: 10.1016/bs.pbr.2021.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The brainstem is a neglected brain area in neurodegenerative diseases, including Alzheimer's and Parkinson's disease, frontotemporal lobar degeneration and autonomic dysfunction. In Depression, several observations have been made in relation to changes in one particular the Dorsal Raphe Nucleus (DRN) which also points toward as key area in various age-related and neurodevelopmental diseases. The DRN is further thought to be related to stress regulated processes and cognitive events. It is involved in neurodegeneration, e.g., amyloid plaques, neurofibrillary tangles, and impaired synaptic transmission in Alzheimer's disease as shown in our autopsy findings. The DRN is a phylogenetically old brain area, with projections that reach out to a large number of regions and nuclei of the central nervous system, particularly in the forebrain. These ascending projections contain multiple neurotransmitters. One of the main reasons for the past and current interest in the DRN is its involvement in depression, and its main transmitter serotonin. The DRN also points toward the increased importance and focus of the brainstem as key area in various age-related and neurodevelopmental diseases. This review describes the morphology, ascending projections and the complex neurotransmitter nature of the DRN, stressing its role as a key research target into the neural bases of depression.
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Affiliation(s)
- Harry W M Steinbusch
- Department of Cellular Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands; Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology-DGIST, Daegu, South Korea.
| | | | - David A Hopkins
- Department of Medical Neuroscience, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
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Balázsfi D, Zelena D, Demeter K, Miskolczi C, Varga ZK, Nagyváradi Á, Nyíri G, Cserép C, Baranyi M, Sperlágh B, Haller J. Differential Roles of the Two Raphe Nuclei in Amiable Social Behavior and Aggression - An Optogenetic Study. Front Behav Neurosci 2018; 12:163. [PMID: 30116182 PMCID: PMC6082963 DOI: 10.3389/fnbeh.2018.00163] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 07/11/2018] [Indexed: 01/10/2023] Open
Abstract
Serotonergic mechanisms hosted by raphe nuclei have important roles in affiliative and agonistic behaviors but the separate roles of the two nuclei are poorly understood. Here we studied the roles of the dorsal (DR) and median raphe region (MRR) in aggression by optogenetically stimulating the two nuclei. Mice received three 3 min-long stimulations, which were separated by non-stimulation periods of 3 min. The stimulation of the MRR decreased aggression in a phasic-like manner. Effects were rapidly expressed during stimulations, and vanished similarly fast when stimulations were halted. No carryover effects were observed in the subsequent three trials performed at 2-day intervals. No effects on social behaviors were observed. By contrast, DR stimulation rapidly and tonically promoted social behaviors: effects were present during both the stimulation and non-stimulation periods of intermittent stimulations. Aggressive behaviors were marginally diminished by acute DR stimulations, but repeated stimulations administered over 8 days considerably decreased aggression even in the absence of concurrent stimulations, indicating the emergence of carryover effects. No such effects were observed in the case of social behaviors. We also investigated stimulation-induced neurotransmitter release in the prefrontal cortex, a major site of aggression control. MRR stimulation rapidly but transiently increased serotonin release, and induced a lasting increase in glutamate levels. DR stimulation had no effect on glutamate, but elicited a lasting increase of serotonin release. Prefrontal serotonin levels remained elevated for at least 2 h subsequent to DR stimulations. The stimulation of both nuclei increased GABA release rapidly and transiently. Thus, differential behavioral effects of the two raphe nuclei were associated with differences in their neurotransmission profiles. These findings reveal a surprisingly strong behavioral task division between the two raphe nuclei, which was associated with a nucleus-specific neurotransmitter release in the prefrontal cortex.
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Affiliation(s)
- Diána Balázsfi
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Dóra Zelena
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Kornél Demeter
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Christina Miskolczi
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Zoltán K Varga
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Ádám Nagyváradi
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Gábor Nyíri
- Laboratory of Cerebral Cortex Research, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Csaba Cserép
- János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary.,Laboratory of Cerebral Cortex Research, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Mária Baranyi
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Beáta Sperlágh
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - József Haller
- Laboratory of Behavioural and Stress Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,Institute of Behavioural Sciences and Law Enforcement, National University of Public Service, Budapest, Hungary
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Gölöncsér F, Baranyi M, Balázsfi D, Demeter K, Haller J, Freund TFF, Zelena D, Sperlágh B. Regulation of Hippocampal 5-HT Release by P2X7 Receptors in Response to Optogenetic Stimulation of Median Raphe Terminals of Mice. Front Mol Neurosci 2017; 10:325. [PMID: 29075178 PMCID: PMC5643475 DOI: 10.3389/fnmol.2017.00325] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 09/27/2017] [Indexed: 01/01/2023] Open
Abstract
Serotonergic and glutamatergic neurons of median raphe region (MRR) play a pivotal role in the modulation of affective and cognitive functions. These neurons synapse both onto themselves and remote cortical areas. P2X7 receptors (P2rx7) are ligand gated ion channels expressed by central presynaptic excitatory nerve terminals and involved in the regulation of neurotransmitter release. P2rx7s are implicated in various neuropsychiatric conditions such as schizophrenia and depression. Here we investigated whether 5-HT release released from the hippocampal terminals of MRR is subject to modulation by P2rx7s. To achieve this goal, an optogenetic approach was used to selectively activate subpopulation of serotonergic terminals derived from the MRR locally, and one of its target area, the hippocampus. Optogenetic activation of neurons in the MRR with 20 Hz was correlated with freezing and enhanced locomotor activity of freely moving mice and elevated extracellular levels of 5-HT, glutamate but not GABA in vivo. Similar optical stimulation (OS) significantly increased [3H]5-HT and [3H]glutamate release in acute MRR and hippocampal slices. We examined spatial and temporal patterns of [3H]5-HT release and the interaction between the serotonin and glutamate systems. Whilst [3H]5-HT release from MRR neurons was [Ca2+]o-dependent and sensitive to TTX, CNQX and DL-AP-5, release from hippocampal terminals was not affected by the latter drugs. Hippocampal [3H]5-HT released by electrical but not OS was subject to modulation by 5- HT1B/D receptors agonist sumatriptan (1 μM), whereas the selective 5-HT1A agonist buspirone (0.1 μM) was without effect. [3H]5-HT released by electrical and optical stimulation was decreased in mice genetically deficient in P2rx7s, and after perfusion with selective P2rx7 antagonists, JNJ-47965567 (0.1 μM), and AZ-10606120 (0.1 μM). Optical and electrical stimulation elevated the extracellular level of ATP. Our results demonstrate for the first time the modulation of 5-HT release from hippocampal MRR terminals by the endogenous activation of P2rx7s. P2rx7 mediated modulation of 5-HT release could contribute to various physiological and pathophysiological phenomena, related to hippocampal serotonergic transmission.
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Affiliation(s)
- Flóra Gölöncsér
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University School of Ph.D. Studies, Budapest, Hungary
| | - Mária Baranyi
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Diána Balázsfi
- János Szentágothai School of Neurosciences, Semmelweis University School of Ph.D. Studies, Budapest, Hungary.,Laboratory of Stress and Behavior Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Kornél Demeter
- Unit of Behavioral Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - József Haller
- Laboratory of Stress and Behavior Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,Unit of Behavioral Studies, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Tamás F F Freund
- Laboratory of Cerebral Cortex, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Dóra Zelena
- Laboratory of Stress and Behavior Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Beáta Sperlágh
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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Regulation of neuronal input transformations by tunable dendritic inhibition. Nat Neurosci 2012; 15:423-30, S1-3. [PMID: 22246433 DOI: 10.1038/nn.3024] [Citation(s) in RCA: 314] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 12/07/2011] [Indexed: 11/08/2022]
Abstract
Transforming synaptic input into action potential output is a fundamental function of neurons. The pattern of action potential output from principal cells of the mammalian hippocampus encodes spatial and nonspatial information, but the cellular and circuit mechanisms by which neurons transform their synaptic input into a given output are unknown. Using a combination of optical activation and cell type-specific pharmacogenetic silencing in vitro, we found that dendritic inhibition is the primary regulator of input-output transformations in mouse hippocampal CA1 pyramidal cells, and acts by gating the dendritic electrogenesis driving burst spiking. Dendrite-targeting interneurons are themselves modulated by interneurons targeting pyramidal cell somata, providing a synaptic substrate for tuning pyramidal cell output through interactions in the local inhibitory network. These results provide evidence for a division of labor in cortical circuits, where distinct computational functions are implemented by subtypes of local inhibitory neurons.
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Puig MV, Gulledge AT. Serotonin and prefrontal cortex function: neurons, networks, and circuits. Mol Neurobiol 2011; 44:449-64. [PMID: 22076606 DOI: 10.1007/s12035-011-8214-0] [Citation(s) in RCA: 265] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 10/17/2011] [Indexed: 02/06/2023]
Abstract
Higher-order executive tasks such as learning, working memory, and behavioral flexibility depend on the prefrontal cortex (PFC), the brain region most elaborated in primates. The prominent innervation by serotonin neurons and the dense expression of serotonergic receptors in the PFC suggest that serotonin is a major modulator of its function. The most abundant serotonin receptors in the PFC, 5-HT1A, 5-HT2A and 5-HT3A receptors, are selectively expressed in distinct populations of pyramidal neurons and inhibitory interneurons, and play a critical role in modulating cortical activity and neural oscillations (brain waves). Serotonergic signaling is altered in many psychiatric disorders such as schizophrenia and depression, where parallel changes in receptor expression and brain waves have been observed. Furthermore, many psychiatric drug treatments target serotonergic receptors in the PFC. Thus, understanding the role of serotonergic neurotransmission in PFC function is of major clinical importance. Here, we review recent findings concerning the powerful influences of serotonin on single neurons, neural networks, and cortical circuits in the PFC of the rat, where the effects of serotonin have been most thoroughly studied.
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Affiliation(s)
- M Victoria Puig
- The Picower Institute for Learning and Memory and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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Blazquez-Llorca L, García-Marín V, DeFelipe J. GABAergic complex basket formations in the human neocortex. J Comp Neurol 2011; 518:4917-37. [PMID: 21031559 DOI: 10.1002/cne.22496] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Certain GABAergic interneurons in the cerebral cortex, basket cells, establish multiple connections with cell bodies that typically outline the somata and proximal dendrites of pyramidal cells. During studies into the distribution of the vesicular GABA transporter (VGAT) in the human cerebral cortex, we were struck by the presence of a very dense, pericellular arrangement of multiple VGAT-immunoreactive (-ir) terminals in certain cortical areas. We called these terminals "Complex basket formations" (Cbk-formations) to distinguish them from the simpler and more typical pericellular GABAergic innervations of most cortical neurons. Here we examined the distribution of these VGAT-ir Cbk-formations in various cortical areas, including the somatosensory (area 3b), visual (areas 17 and 18), motor (area 4), associative frontal (dorsolateral areas 9, 10, 45, 46, and orbital areas 11, 12, 13, 14, 47), associative temporal (areas 20, 21, 22, and 38), and limbic cingulate areas (areas 24, 32). Furthermore, we used dual or triple staining techniques to study the chemical nature of the innervated cells. We found that VGAT-ir Cbk-formations were most frequently found in area 4 followed by areas 3b, 13, and 18. In addition, they were mostly observed in layer III, except in area 17, where they were most dense in layer IV. We also found that 70% of the innervated neurons were pyramidal cells, while the remaining 30% were multipolar cells. Most of these multipolar cells expressed the calcium-binding protein parvalbumin and the lectin Vicia villosa agglutinin.
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Descarries L, Riad M, Parent M. Ultrastructure of the Serotonin Innervation in the Mammalian Central Nervous System. HANDBOOK OF BEHAVIORAL NEUROSCIENCE 2010. [DOI: 10.1016/s1569-7339(10)70072-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Jackson J, Bland BH, Antle MC. Nonserotonergic projection neurons in the midbrain raphe nuclei contain the vesicular glutamate transporter VGLUT3. Synapse 2009; 63:31-41. [PMID: 18925658 DOI: 10.1002/syn.20581] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The brainstem raphe nuclei are typically assigned a role in serotonergic brain function. However, numerous studies have reported that a large proportion of raphe projection cells are nonserotonergic. The identity of these projection cells is unknown. Recent studies have reported that the vesicular glutamate transporter VGLUT3 is found in both serotonergic and nonserotonergic neurons in both the median raphe (MR) and dorsal raphe (DR) nuclei. We injected the retrograde tracer cholera toxin subunit B into either the dorsal hippocampus or the medial septum (MS) and used triple labeled immunofluorescence to determine if nonserotonergic raphe cells projecting to these structures contained VGLUT3. Consistent with previous studies, only about half of retrogradely labeled MR neurons projecting to the hippocampus contained serotonin, whereas a majority of the retrogradely labeled nonserotonergic cells contained VGLUT3. Similar patterns were observed for MR cells projecting to the MS. About half of retrogradely labeled nonserotonergic neurons in the DR contained VGLUT3. Additionally, a large number of retrogradely labeled cells in the caudal linear and interpeduncular nuclei projecting to the MS were found to contain VGLUT3. These data suggest the enigmatic nonserotonergic projection from the MR to forebrain regions may be glutamatergic. In addition, these results demonstrate a dissociation between glutamatergic and serotonergic MR afferent inputs to the MS and hippocampus suggesting divergent and/or complementary roles of these pathways in modulating cellular activity within the septohippocampal network.
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Affiliation(s)
- Jesse Jackson
- Behavioral Neuroscience Research Group, Department of Psychology, University of Calgary, Calgary, Alberta, Canada
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Decrease in REM latency and changes in sleep quality parallel serotonergic damage and recovery after MDMA: a longitudinal study over 180 days. Int J Neuropsychopharmacol 2008; 11:795-809. [PMID: 18261250 DOI: 10.1017/s1461145708008535] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The recreational drug ecstasy [3,4-methylenedioxymethamphetamine (MDMA)], has been found to selectively damage brain serotonin neurons in experimental animals, and probably in human MDMA users, but detailed morphometric analyses and parallel functional measures during damage and recovery are missing. Since there is evidence that serotonin regulates sleep, we have compared serotonergic markers parallel with detailed analysis of sleep patterns at three time-points within 180 d after a single dose of 15 mg/kg MDMA in male Dark Agouti rats. At 7 d and 21 d after MDMA treatment, significant(30-40%), widespread reductions in serotonin transporter (5-HTT) density were detected in the cerebral cortex, hippocampus, most parts of the hypothalamus, and some of the brainstem nuclei. With the exception of the hippocampus, general recovery was observed in the brain 180 d after treatment. Transient increases followed by decreases were detected in 5-HTT mRNA expression of dorsal and median raphe nuclei at 7 d and 21 d after the treatment. Significant reductions in rapid eye movement (REM) sleep latency, increases in delta power spectra in non-rapid eye movement sleep and increased fragmentation of sleep were also detected, but all these alterations disappeared by the 180th day. The present data provide evidence for long-term, albeit, except for the hippocampus, transient changes in the terminal and cellular regions of the serotonergic system after this drug. Reduced REM latency and increased sleep fragmentation are the most characteristic alterations of sleep consistently described in depression using EEG sleep polygraphy.
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Michelsen KA, Schmitz C, Steinbusch HWM. The dorsal raphe nucleus—From silver stainings to a role in depression. ACTA ACUST UNITED AC 2007; 55:329-42. [PMID: 17316819 DOI: 10.1016/j.brainresrev.2007.01.002] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 01/09/2007] [Accepted: 01/10/2007] [Indexed: 11/29/2022]
Abstract
Over a hundred years ago, Santiago Ramón y Cajal used a new staining method developed by Camillo Golgi to visualize, among many other structures, what we today call the dorsal raphe nucleus (DRN) of the midbrain. Over the years, the DRN has emerged as a multifunctional and multitransmitter nucleus, which modulates or influences many CNS processes. It is a phylogenetically old brain area, whose projections reach out to a large number of regions and nuclei of the CNS, particularly in the forebrain. Several DRN-related discoveries are tightly connected with important events in the history of neuroscience, for example the invention of new histological methods, the discovery of new neurotransmitter systems and the link between neurotransmitter function and mood disorders. One of the main reasons for the wide current interest in the DRN is the nucleus' involvement in depression. This involvement is particularly attributable to the main transmitter of the DRN, serotonin. Starting with a historical perspective, this essay describes the morphology, ascending projections and multitransmitter nature of the DRN, and stresses its role as a key target for depression research.
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Affiliation(s)
- Kimmo A Michelsen
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands
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Raghanti MA, Stimpson CD, Marcinkiewicz JL, Erwin JM, Hof PR, Sherwood CC. Differences in Cortical Serotonergic Innervation among Humans, Chimpanzees, and Macaque Monkeys: A Comparative Study. Cereb Cortex 2007; 18:584-97. [PMID: 17586605 DOI: 10.1093/cercor/bhm089] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In this study, we assess the possibility that the evolution of human intellectual capacities was supported by changes in the supply of serotonin to the frontal cortex. To this end, quantitative comparative analyses were performed among humans, chimpanzees, and macaques. Immunohistochemical methods were used to visualize serotonin transporter-immunoreactive (SERT-ir) axons within the cerebral cortex. Areas 9 and 32 were chosen for evaluation due to their roles in working memory and theory of mind, respectively. Primary motor cortex was also evaluated because it is not associated with higher cognitive functions. The findings revealed that humans do not display a quantitative increase in serotonin innervation. However, the results indicated region- and layer-specific differences among species in serotonergic innervation pattern. Compared with macaques, humans and chimpanzees together displayed a greater density of SERT-ir axons relative to neuron density in layers V/VI. This change was detected in cortical areas 9 and 32, but not in primary motor cortex. Further, morphological specializations, coils of axons, were observed in humans and chimpanzees that were absent in macaques. These features may represent a greater capacity for cortical plasticity exclusive to hominoids. Taken together, these results indicate a significant reorganization of cortical serotonergic transmission in humans and chimpanzees.
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Affiliation(s)
- Mary Ann Raghanti
- Department of Anthropology and School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA.
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Jarnot M, Corbett AM. Immunolocalization of NaV1.2 channel subtypes in rat and cat brain and spinal cord with high affinity antibodies. Brain Res 2006; 1107:1-12. [PMID: 16815341 DOI: 10.1016/j.brainres.2006.05.090] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 05/24/2006] [Accepted: 05/26/2006] [Indexed: 11/29/2022]
Abstract
High titer polyclonal antibodies were produced in rabbit against a peptide unique to NaV1.2 sodium channels. NaV1.2 antibodies displayed 500,000-fold greater affinity for the NaV1.2 peptide compared with NaV1.1 or NaV1.3 peptides from the same region. These antibodies, when coupled to Sepharose beads, retained saxitoxin binding sites from solubilized rat brain membranes. Eluted protein from this antibody-affinity column was recognized by antibodies directed against neuronal voltage-gated sodium channels. Rabbit antibodies, which had been partially purified, were used in immunocytochemical localization of the NaV1.2 channel in 50 microm rat brain slices at dilutions of 1:1000 or 1:2000. NaV1.2 channels were predominately localized in unmyelinated fibers in the cortex, hippocampus, spinal cord and hypothalamus. Varicosities were seen in fiber staining which may reflect true varicosities in the fiber or simply varying densities of sodium channels along the fiber. Cell body staining with the NaV1.2 antibody was primarily observed in the hypothalamus. Antibody staining in the cerebellum was complex, with staining observed primarily in posterior lobes and considerably lower amounts of staining observed in anterior lobes. Specific staining was limited to fibers located in the granule and molecular layer, in an orientation consistent with granule cell unmyelinated axon labeling.
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Affiliation(s)
- Miranda Jarnot
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, 3640 Col. Glenn Highway, Dayton, OH 45435, USA
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Keuker JIH, Keijser JN, Nyakas C, Luiten PGM, Fuchs E. Aging is accompanied by a subfield-specific reduction of serotonergic fibers in the tree shrew hippocampal formation. J Chem Neuroanat 2005; 30:221-9. [PMID: 16169187 DOI: 10.1016/j.jchemneu.2005.08.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 07/07/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
The hippocampal formation is a crucial structure for learning and memory, and serotonin together with other neurotransmitters is essential in these processes. Although the effects of aging on various neurotransmitter systems in the hippocampus have been extensively investigated, it is not entirely clear whether or how the hippocampal serotonergic innervation changes during aging. Rat studies, which have mostly focused on aging-related changes in the dentate gyrus, have implied a loss of hippocampal serotonergic fibers. We used the tree shrew (Tupaia belangeri), an intermediate between insectivores and primates, as a model of aging. We applied immunocytochemistry with an antibody against serotonin to assess serotonergic fiber densities in the various hippocampal subfields of adult (0.9-1.3 years) and old (5-7 years) tree shrews. Our results have revealed a reduction of serotonergic fiber densities in the stratum radiatum of CA1 and CA3, and in the stratum oriens of CA3. A partial depletion of serotonin in the hippocampal formation, as can be expected from our current observations, will probably have an impact on the functioning of hippocampal principal neurons. Our findings also indicate that the rat and the tree shrew hippocampal serotonergic innervation show some variations that seem to be differentially affected during aging.
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Affiliation(s)
- Jeanine I H Keuker
- Clinical Neurobiology Laboratory, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany.
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Bjarkam CR, Sørensen JC, Geneser FA. Distribution and morphology of serotonin-immunoreactive axons in the retrohippocampal areas of the New Zealand white rabbit. ACTA ACUST UNITED AC 2005; 210:199-207. [PMID: 16170538 DOI: 10.1007/s00429-005-0004-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/08/2005] [Indexed: 12/19/2022]
Abstract
This study provides a detailed light microscopic description of the morphology and distribution of serotonin-immunoreactive axons in the paleocortical retrohippocampal areas, viz. the subiculum, presubiculum, parasubiculum and entorhinal area, and the adjoining neocortical perirhinal and retrosplenial cortices of the New Zealand white rabbit. Serotonergic axons could be segregated into three different fiber types named fine fibers, beaded fibers and stem-axons. Fine fibers were evenly distributed thin axons with small fusiform/granular varicosities. Beaded fibers were thin axons with large varicosities, predominantly located in the retrohippocampal supragranular layers, where they often formed pericellular arrays. Stem-axons were thick straight, nonvaricose axons seen in the white matter of psalterium dorsale, alveus and the plexiform layer. The paleocortical retrohippocampal areas had a dense supragranular innervation with numerous tortuous fine and beaded fibers, intermingled in conglomerates with conspicuous varicosities forming pericellular arrays. In contrast, the neocortical area 17 and the lateral part of the perirhinal cortex (area 36) were innervated by evenly distributed fine fibers with a moderate number of small varicosities and few ramifications, whereas, the retrosplenial cortex (areas 29e, 29ab and 29cd), and the medial part of the perirhinal cortex (area 35) displayed an intermediate innervation pattern, probably reflecting the transitional nature of these areas being located between the paleo- and the neocortex. The described dualistic innervation pattern may functionally enable the serotonergic system to exert a strong influence on the supragranular layers of the retrohippocampal areas and thus on the neural input entering these areas from the perirhinal and neighboring polymodal association neocortices, whereas the innervation pattern in the adjoining neocortical areas points towards a more diffuse and general modulation of neural activity herein.
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Affiliation(s)
- Carsten R Bjarkam
- Department of Neurobiology, Institute of Anatomy, University of Aarhus, 8000 Aarhus C, Denmark.
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Williams SM, Bryan-Lluka LJ, Pow DV. Quantitative analysis of immunolabeling for serotonin and for glutamate transporters after administration of imipramine and citalopram. Brain Res 2005; 1042:224-32. [PMID: 15854594 DOI: 10.1016/j.brainres.2005.02.045] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Revised: 02/14/2005] [Accepted: 02/15/2005] [Indexed: 11/21/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is an amine neurotransmitter derived from tryptophan and is important in brain systems regulating mood, emotional behavior, and sleep. Selective serotonin reuptake inhibitor (SSRI) drugs are used to treat disorders such as depression, stress, eating disorders, autism, and schizophrenia. It is thought that these drugs act to prolong the action of 5-HT by blocking reuptake. This may lead to decreased 5-HT content in the nerve fibers themselves; however, this has not previously been directly demonstrated. We have studied the effects of administration of two drugs, imipramine and citalopram, on levels of 5-HT in nerve fibers in the murine brain. Quantitative analysis of the areal density of 5-HT fibers throughout the brain was performed using ImageJ software. While a high density of fibers was observed in mid- and hind-brain regions and areas such as thalamus and hypothalamus, densities were far lower in areas such as cortex, where SSRIs might be thought to exert their actions. As anticipated, imipramine and citalopram produced a decline in 5-HT levels in nerve fibers, but the result was not uniform. Areas such as inferior colliculus showed significant reduction whereas little, if any, change was observed in the adjacent superior colliculus. The reason for, and significance of, this regionality is unclear. It has been proposed that serotonin effects in the brain might be linked to changes in glutamatergic transmission. Extracellular glutamate levels are regulated primarily by glial glutamate transporters. Qualitative evaluation of glutamate transporter immunolabeling in cortex of control and drug-treated mice revealed no discernable difference in intensity of glutamate transporter immunoreactivity. These data suggest that changes in intracellular and extracellular levels of serotonin do not cause concomitant changes in astroglial glutamate transporter expression, and thus cannot represent a mechanism for the delayed efficacy of antidepressants when administered clinically.
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Affiliation(s)
- Susan M Williams
- Discipline of Anatomy, School of Biomedical Sciences, and Hunter Medical Research Institute (HMRI), University of Newcastle, Callaghan, NSW, 2308, Australia
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18
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Abstract
The raphe nuclei are distributed near the midline of the brainstem along its entire rostro-caudal extension. The serotonergic neurons are their main neuronal components, although a proportion of them lie in subdivisions of the lateral reticular formation. They develop from mesopontine and medullary primordia, and the resulting grouping into rostral and caudal clusters is maintained into adulthood, and is reflected in the connectivity. Thus, the mesencephalon and rostral pons, neurons within the rostral raphe complex (caudal linear, dorsal raphe, and median raphe nuclei) project primarily to the forebrain. By contrast, in the caudal pons and medulla oblongata, neurons within the caudal raphe complex (raphe magnus, raphe obscurus, raphe pallidus nuclei and parts of the adjacent lateral reticular formation) project to the brainstem nuclei and to the spinal cord. The median raphe and dorsal raphe nuclei provide parallel and overlapping projections to many forebrain structures with axon fibers exhibiting distinct structural and functional characteristics. The caudal group of the serotonergic system projects to the brainstem, and, by three parallel projections, to the dorsal, intermediate and ventral columns in the spinal cord. The serotonergic axons arborize over large areas comprising functionally diverse targets. Some projections form classical chemical synapses while many do not, thus contributing to the so-called paracrine or volume transmission. The serotonergic projections participate in the regulation of different functional (motor, somatosensory, limbic) systems; and have been associated with a wide range of neuropsychiatric and neurological disorders. Finally, recent experimental data support the role of serotonin in modulating brain development, such that a dysfunction in serotonergic transmission during early life could lead to long lasting structural and functional alterations.
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Affiliation(s)
- Jean-Pierre Hornung
- Institut de biologie cellulaire et de morphologie, University of Lausanne, Rue du Bugnon 9, 1005, Lausanne, Switzerland.
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19
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Djavadian RL, Wielkopolska E, Turlejski K. Neonatal depletion of serotonin increases the numbers of callosally projecting neurons in cat visual areas 17 and 18. Neurosci Lett 2004; 351:91-4. [PMID: 14583389 DOI: 10.1016/j.neulet.2003.07.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We investigated the influence of neonatal depletion of serotonin on the developmental reduction of callosal connections in cat visual cortex. Neonatal kittens were injected with 5,7-dihydroxytryptamine. At the age of 3 months, Fast Blue was injected into visual areas of one hemisphere in these and control cats and retrogradely labeled perikarya were mapped in the opposite hemisphere. In both groups callosally projecting neurons were found in a 3-5 mm wide belt centered on the transient zone of areas 17 and 18. However, numbers of labeled neurons were twice higher in the serotonin-depleted cats. We postulate that normally serotonin intensifies the process of axon pruning by augmenting developmental plasticity, therefore its depletion reduced the plasticity and more axons targeting callosal zones were stabilized, even though ectopic projections were still eliminated.
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Affiliation(s)
- R L Djavadian
- Department of Neurophysiology, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093, Warsaw, Poland.
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20
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Bjarkam CR, Sørensen JC, Geneser FA. Distribution and morphology of serotonin-immunoreactive axons in the hippocampal region of the New Zealand white rabbit. I. Area dentata and hippocampus. Hippocampus 2003; 13:21-37. [PMID: 12625454 DOI: 10.1002/hipo.10042] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This study provides a detailed light microscopic description of the morphology and distribution of immunohistochemically stained serotonergic axons in the hippocampal region of the New Zealand white rabbit. The serotonergic axons were segregated morphologically into three types: beaded fibers, fine fibers, and stem-axons, respectively. Beaded fibers were thin serotonergic axons with large varicosities, whereas thin axons with small fusiform or granular varicosities were called fine fibers. Finally, thick straight non-varicose axons were called stem-axons. Beaded fibers often formed large conglomerates with numerous boutons (pericellular arrays) in close apposition to the cell-rich layers in the hippocampal region, e.g., the granular and hilar cell layers of the dentate area and the pyramidal cell layer ventrally in CA3. The pericellular arrays in these layers were often encountered in relation to small calbindin-D2BK-positive cells, as shown by immunohistochemical double staining for serotonin and calbindin-D28K. The beaded and fine serotonergic fibers displayed a specific innervation pattern in the hippocampal region and were encountered predominantly within the terminal field of the perforant path, e.g., the stratum moleculare hippocampi and the outer two-thirds of the dentate molecular layer. These fibers were also frequently seen in the deep part of the stratum oriens and the alveus, forming a dense plexus in relation to large multipolar calbindin-D28K-positive cells and their basal extensions. Stem-axons were primarily seen in the fimbria and alveus. This innervation pattern was present throughout the entire hippocampal formation, but there were considerable septotemporal differences in the density of the serotonergic innervation. A high density of innervation prevailed in the ventral/temporal part of the hippocampal formation, whereas the dorsal/septal part received only a moderate to weak serotonergic innervation. These results suggest that the serotonergic system could modulate the internal hippocampal circuitry by way of its innervation in the terminal field of the perforant path, the hilus fasciae dentatae, and ventrally in the zone closely apposed to the mossy fiber layer and the pyramidal cells of CA3. This modulation could be of a dual nature, mediated directly by single serotonergic fibers traversing the hippocampal layers or indirectly by the pericellular arrays and their close relation to the calbindin-D28K-positive cells. The marked septotemporal differences in innervation density point toward a difference between the ventral and dorsal parts of the hippocampal formation with respect to serotonergic function and need for serotonergic modulation.
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Affiliation(s)
- Carsten R Bjarkam
- Department of Neurobiology, Institute of Anatomy, University of Aarhus, Denmark.
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21
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Abstract
Numerous observations suggest diverse and modulatory roles for serotonin (5-HT) in cortex. Because of the diversity of cell types and multiple receptor subtypes and actions of 5-HT, it has proven difficult to determine the overall role of 5-HT in cortical function. To provide a broader perspective of cellular actions, we studied the effects of 5-HT on morphologically and physiologically identified pyramidal and nonpyramidal neurons from layers I-III of primary somatosensory and motor cortex. We found cell type-specific differences in response to 5-HT. Four cell types were observed in layer I: Cajal Retzius, pia surface, vertical axon, and horizontal axon cells. The physiology of these cells ranged from fast spiking (FS) to regular spiking (RS). In layers II-III, we observed interneurons with FS, RS, and late spiking physiology. Morphologically, these cells varied from bipolar to multipolar and included basket-like and chandelier cells. 5-HT depolarized or hyperpolarized pyramidal neurons and reduced the slow afterhyperpolarization and spike frequency. Consistent with a role in facilitating tonic inhibition, 5-HT2 receptor activation increased the frequency of spontaneous IPSCs in pyramidal neurons. In layers II-III, 70% of interneurons were depolarized by 5-HT. In layer I, 57% of cells with axonal projections to layers II-III (vertical axon) were depolarized by 5-HT, whereas 63% of cells whose axons remain in layer I (horizontal axon) were hyperpolarized by 5-HT. We propose a functional segregation of 5-HT effects on cortical information processing, based on the pattern of axonal arborization.
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5-HT3 receptors mediate serotonergic fast synaptic excitation of neocortical vasoactive intestinal peptide/cholecystokinin interneurons. J Neurosci 2002. [PMID: 12196560 DOI: 10.1523/jneurosci.22-17-07389.2002] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neocortical neurons expressing the serotonin 5-HT3 receptor (5-HT3R) were characterized in rat acute slices by using patch-clamp recordings combined with single-cell RT-PCR and histochemical labeling. The 5-HT3A receptor subunit was expressed selectively in a subset of GABAergic interneurons coexpressing cholecystokinin (CCK) and vasoactive intestinal peptide (VIP). The 5-HT3B subunit was never detected, indicating that 5-HT3Rs expressed by neocortical interneurons did not contain this subunit. In 5-HT3A-expressing VIP/CCK interneurons, serotonin induced fast membrane potential depolarizations by activating an inward current that was blocked by the selective 5-HT3R antagonist tropisetron. Furthermore, we observed close appositions between serotonergic fibers and the dendrites and somata of 5-HT3R-expressing neurons, suggestive of possible synaptic contacts. Indeed, in interneurons exhibiting rapid excitation by serotonin, local electrical stimulations evoked fast EPSCs of large amplitude that were blocked by tropisetron. Finally, 5-HT3R-expressing neurons were also excited by a nicotinic agonist, indicating that serotonergic and cholinergic fast synaptic transmission could converge onto VIP/CCK interneurons. Our results establish a clear correlation between the presence of the 5-HT3A receptor subunit in neocortical VIP/CCK GABAergic interneurons, its functional expression, and its synaptic activation by serotonergic afferent fibers from the brainstem raphe nuclei.
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Okhotin VE, Kalinichenko SG. The histophysiology of neocortical basket cells. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2002; 32:455-70. [PMID: 12402997 DOI: 10.1023/a:1019899903876] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- V E Okhotin
- Laboratory for Neurogenetics and Developmental Genetics, Institute of Gene Biology, Russian Academy of Sciences, Moscow
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Halasy K, Miettinen R, Szabat E, Freund TF. GABAergic Interneurons are the Major Postsynaptic Targets of Median Raphe Afferents in the Rat Dentate Gyrus. Eur J Neurosci 2002; 4:144-153. [PMID: 12106377 DOI: 10.1111/j.1460-9568.1992.tb00861.x] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The termination pattern of median raphe axons was studied in the rat dentate gyrus using Phaseolus vulgaris leucoagglutinin as an anterograde tracer, in combination with postembedding immunostaining for gamma-amino-butyric acid (GABA), and pre-embedding immunostaining for calbindin D28k, parvalbumin and GABA. Postembedding immunogold staining for GABA revealed that the majority (73.7%) of anterogradely labelled median raphe boutons make synaptic contacts with GABA-immunoreactive postsynaptic targets, mainly with dendritic shafts and perikarya. Pre-embedding immunocytochemical double staining for the anterograde tracer and GABA confirmed the electron microscopic results and showed that varicose median raphe axons establish multiple contacts with fusiform interneurons in the hilus and different types of basket cells in the granule cell layer. Some of the innervated cells were shown to contain calbindin D28k, whereas GABAergic interneurons containing another calcium-binding protein, parvalbumin, were never seen to receive multiple contacts from axons of raphe origin. Our results suggest that serotonergic median raphe fibres influence the firing of dentate granule cells via local inhibitory interneurons. The mechanism of using these interneurons with extensive local connections as monosynaptic targets may explain the great efficacy of this pathway in the control of hippocampal electrical activity.
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Affiliation(s)
- K. Halasy
- Institute of Experimental Medicine, Hungarian Academy of Sciences, PO Box 67, Budapest, H-1450 Hungary
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25
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Abstract
The claustrum is reciprocally and topographically connected with all functional areas of the cerebral cortex. Different cortical areas differ in the source, density, and laminar distribution of serotonergic innervation, with visual cortex receiving an especially rich serotonergic innervation. We asked if there were likewise differences in serotonergic innervation in different regions of the claustrum. We analyzed 50-microm coronal sections through the claustrum of the macaque monkey processed using standard immunohistochemical techniques and an antibody to serotonin. We found labeled fibers throughout the dorsal-ventral and anterior-posterior extent of the claustrum. A few fibers were relatively straight and lacked varicosities. Most fibers had varicosities; the size, shape, and spacing of varicosities varied among fibers and even along a single fiber. Some stained fibers partially encircled cells, and varicosities were seen in close apposition to the cell bodies. There was a major difference between dorsal and ventral claustrum in the pattern of stained fibers. In the ventral, visual, claustrum, stained segments of axons were short and randomly arranged relative to each other, and there were many stained puncta. In the more dorsal, nonvisual claustrum, many fibers ran in a dorsal-ventral direction, along the long axis of the claustrum, and could be followed for long distances.
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Affiliation(s)
- J S Baizer
- Department of Physiology and Biophysics, University at Buffalo, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, NY 14214, USA.
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26
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Paspalas CD, Papadopoulos GC. Serotoninergic afferents preferentially innervate distinct subclasses of peptidergic interneurons in the rat visual cortex. Brain Res 2001; 891:158-67. [PMID: 11164819 DOI: 10.1016/s0006-8993(00)03193-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although it is well documented that the non-pyramidal neurons of the cerebral cortex are under the influence of the vast serotoninergic input, the ultrastructural substrate for such functional interactions appears largely obscure. We sought to address this issue by dual immunoelectron microscopy, combining antibodies against serotonin (5-HT) and three neurochemical markers for peptidergic interneurons, namely somatostatin (SRIF), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP). The gold-substituted silver-peroxidase method was employed to intensify and differentiate the end-product of the peptide-immunoreaction from the non-intensified 5-HT fibers. Mainly the SRIF but also the NPY neurons were encountered among the postsynaptic targets of the 5-HT boutons. Recipients of synapses were perikarya and proximal dendrites of SRIF and NPY cells but also distal dendrites of the SRIF neurons. Neither synaptic relationships nor close appositions were ever identified between 5-HT boutons and VIP-immunoreactive elements. This remarkable synaptic preference/avoidance of 5-HT afferents for specific peptidergic subpopulations reveals a 'wired' component of cortical serotonin neurotransmission, which should be carefully interpreted within the frame of the available literature for extrasynaptic serotonin release.
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Affiliation(s)
- C D Paspalas
- Department of Anatomy and Histology, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, 54006, Thessaloniki, Greece
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27
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Leger L, Charnay Y, Hof PR, Bouras C, Cespuglio R. Anatomical distribution of serotonin-containing neurons and axons in the central nervous system of the cat. J Comp Neurol 2001. [DOI: 10.1002/cne.1133] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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28
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Künzle H, Radtke-Schuller S. Basal telencephalic regions connected with the olfactory bulb in a Madagascan hedgehog tenrec. J Comp Neurol 2000; 423:706-26. [PMID: 10880998 DOI: 10.1002/1096-9861(20000807)423:4<706::aid-cne13>3.0.co;2-#] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In an attempt to gain insight into the organization and evolution of the basal forebrain, the region was analysed cytoarchitecturally, chemoarchitecturally, and hodologically in a lower placental mammal, the lesser hedgehog tenrec. Particular emphasis was laid on the subdivision of the olfactory tubercle, the nuclear complex of the diagonal band, and the cortical amygdala. The proper tubercule and the rostrolateral tubercular seam differed from each other with regard to their immunoreactivity to calbindin and calretinin, as well as their afferents from the piriform cortex. Interestingly, the tubercular seam showed similar properties to the dwarf cell compartment, located immediately adjacent to the islands of Calleja. The most prominent input to the olfactory bulb (OfB) originated from the diagonal nuclear complex. This projection was ipsilateral, whereas the bulbar afferents from the hypothalamus and the mesopontine tegmentum were bilateral. The amygdala projected only sparsely to the OfB, but received a prominent bulbar projection. An exception was the nucleus of the lateral olfactory tract, which was poorly connected with the OfB. Unlike other species with an accessory OfB, the projections from the tenrec's main OfB did not show a topographic organization upon the lateral and medial olfactory amygdala. However, there was an accessory amygdala, which could be differentiated from the lateral nuclei by its intense reaction to NADPh-diaphorase. This reaction was poor in the diagonal nuclear complex as in monkey but unlike in rat. The variability of cell populations and olfactory bulb connections shown here may help to clarify both phylogenetic relationships and the significance of individual basal telencephalic subdivisions.
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Affiliation(s)
- H Künzle
- Institute of Anatomy, University of Munich, D-80336 Munich, Germany
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29
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Bai F, Lau SS, Monks TJ. Glutathione and N-acetylcysteine conjugates of alpha-methyldopamine produce serotonergic neurotoxicity: possible role in methylenedioxyamphetamine-mediated neurotoxicity. Chem Res Toxicol 1999; 12:1150-7. [PMID: 10604863 DOI: 10.1021/tx990084t] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Direct injection of either 3,4-(+/-)-methylenedioxymethamphetamine (MDMA) or 3,4-(+/-)-methylenedioxyamphetamine (MDA) into the brain fails to reproduce the serotonergic neurotoxicity seen following peripheral administration. The serotonergic neurotoxicity of MDA and MDMA therefore appears to be dependent upon the generation of a neurotoxic metabolite, or metabolites, the identity of which remains unclear. alpha-Methyldopamine (alpha-MeDA) is a major metabolite of both MDA and MDMA. We have shown that intracerebroventricular (icv) injection of 2,5-bis(glutathion-S-yl)-alpha-methyldopamine [2, 5-bis(glutathion-S-yl)-alpha-MeDA] causes decreases in serotonin concentrations in the striatum, cortex, and hippocampus, and neurobehavioral effects similar to those seen following MDA and MDMA administration. In contrast, although 5-(glutathion-S-yl)-alpha-methyldopamine [5-(glutathion-S-yl)-alpha-MeDA] and 5-(N-acetylcystein-S-yl)-alpha-methyldopamine [5-(N-acetylcystein-S-yl)-alpha-MeDA] produce neurobehavioral changes similar to those seen with MDA and MDMA, and acute changes in brain 5-HT and dopamine concentrations, neither conjugate caused long-term decreases in 5-HT concentrations. We now report that direct intrastriatal or intracortical administration of 5-(glutathion-S-yl)-alpha-MeDA (4 x 200 or 4 x 400 nmol), 5-(N-acetylcystein-S-yl)-alpha-MeDA (4 x 7 or 4 x 20 nmol), and 2, 5-bis(glutathion-S-yl)-alpha-MeDA (4 x 150 or 4 x 300 nmol) causes significant decreases in striatal and cortical 5-HT concentrations (7 days following the last injection). Interestingly, intrastriatal injection of 5-(glutathion-S-yl)-alpha-MeDA or 2, 5-bis(glutathion-S-yl)-alpha-MeDA, but not 5-(N-acetylcystein-S-yl)-alpha-methyldopamine, also caused decreases in 5-HT concentrations in the ipsilateral cortex. The same pattern of changes was seen when the conjugates were injected into the cortex. The effects of the thioether conjugates of alpha-MeDA were confined to 5-HT nerve terminal fields, since no significant changes in monoamine neurotransmitter levels were detected in brain regions enriched with 5-HT cell bodies (midbrain/diencephalon/telencephalon and pons/medulla). In addition, the effects of the conjugates were selective with respect to the serotonergic system, as no significant changes were seen in dopamine or norepinephrine concentrations. The results indicate that thioether conjugates of alpha-MeDA are selective serotonergic neurotoxicants. Nonetheless, a role for these conjugates in the toxicity observed following systemic administration of MDA and MDMA remains to be demonstrated, and requires further experimentation.
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Affiliation(s)
- F Bai
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, USA
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30
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Zhou FM, Hablitz JJ. Activation of serotonin receptors modulates synaptic transmission in rat cerebral cortex. J Neurophysiol 1999; 82:2989-99. [PMID: 10601434 DOI: 10.1152/jn.1999.82.6.2989] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The cerebral cortex receives an extensive serotonergic (5-hydroxytryptamine, 5-HT) input. Immunohistochemical studies suggest that inhibitory neurons are the main target of 5-HT innervation. In vivo extracellular recordings have shown that 5-HT generally inhibited cortical pyramidal neurons, whereas in vitro studies have shown an excitatory action. To determine the cellular mechanisms underlying the diverse actions of 5-HT in the cortex, we examined its effects on cortical inhibitory interneurons and pyramidal neurons. We found that 5-HT, through activation of 5-HT(2A) receptors, induced a massive enhancement of spontaneous inhibitory postsynaptic currents (sIPSCs) in pyramidal neurons, lasting for approximately 6 min. In interneurons, this 5-HT-induced enhancement of sIPSCs was much weaker. Activation of 5-HT(2A) receptors also increased spontaneous excitatory postsynaptic currents (sEPSCs) in pyramidal neurons. This response desensitized less and at a slower rate. In contrast, 5-HT slightly decreased evoked IPSCs (eIPSCs) and eEPSCs. In addition, 5-HT via 5-HT(3) receptors evoked a large and rapidly desensitizing inward current in a subset of interneurons and induced a transient enhancement of sIPSCs. Our results suggest that 5-HT has widespread effects on both interneurons and pyramidal neurons and that a short pulse of 5-HT is likely to induce inhibition whereas the prolonged presence of 5-HT may result in excitation.
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Affiliation(s)
- F M Zhou
- Department of Neurobiology, University of Alabama, Birmingham, Alabama 35294, USA
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31
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Leranth C, Vertes RP. Median raphe serotonergic innervation of medial septum/diagonal band of Broca (MSDB) parvalbumin-containing neurons: Possible involvement of the MSDB in the desynchronization of the hippocampal EEG. J Comp Neurol 1999. [DOI: 10.1002/(sici)1096-9861(19990809)410:4<586::aid-cne6>3.0.co;2-h] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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32
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Morin LP, Meyer-Bernstein EL. The ascending serotonergic system in the hamster: comparison with projections of the dorsal and median raphe nuclei. Neuroscience 1999; 91:81-105. [PMID: 10336062 DOI: 10.1016/s0306-4522(98)00585-5] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The ascending serotonergic projections are derived largely from the midbrain median and dorsal raphe nuclei, and contribute to the regulation of many behavioral and physiological systems. Serotonergic innervation of the hamster circadian system has been shown to be substantially different from earlier results obtained with other methods and species. The present study was conducted to determine whether similar differences are observed in other brain regions. Ascending projections from the hamster dorsal or median raphe were identified using an anterograde tracer, Phaseolus vulgans leucoagglutinin, injected by iontophoresis into each nucleus. Brains were processed for tracer immunoreactivity, and drawings were made of the median raphe and dorsal raphe efferent projection patterns. The efferents were also compared to the distribution of normal serotonergic innervation of the hamster midbrain and forebrain. The results show widespread, overlapping projection patterns from both the median and dorsal raphe, with innervation generally greater from the dorsal raphe. In several brain regions, including parts of the pretectum, lateral geniculate and basal forebrain, nuclei are innervated by the dorsal, but not the median, raphe. The hypothalamic suprachiasmatic nucleus is the only site innervated exclusively by the median and not by the dorsal raphe. The pattern of normal serotonin fiber and terminal distribution is generally more robust than would be inferred from the anterograde tracer material. However, there is good qualitative similarity between the two sets of data. The oculomotor nucleus and the medial habenula are unusual to the extent that each has a moderately dense serotonin terminal plexus, although neither receives innervation from the median or dorsal raphe. In contrast, the centrolateral thalamic nucleus and lateral habenula have little serotonergic innervation, but receive substantial other neural input from the raphe nuclei. The normal serotonergic innervation of the hamster brain is similar to that in the rat, although there are exceptions. The anterograde tracing of ascending median or dorsal raphe projections reveals a high, but imperfect, degree of correspondence with the serotonin innervation data, and with data from rats derived from immunohistochemical and autoradiographic tract-tracing techniques.
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Affiliation(s)
- L P Morin
- Department of Psychiatry, Stony Brook University, NY 11794, USA
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33
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34
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Morrison J, Hof P, Huntley G. Neurochemical organization of the primate visual cortex. HANDBOOK OF CHEMICAL NEUROANATOMY 1998. [DOI: 10.1016/s0924-8196(98)80004-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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35
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Bjarkam CR, S�rensen JC, Geneser FA. Distribution and morphology of serotonin-immunoreactive neurons in the brainstem of the New Zealand white rabbit. J Comp Neurol 1997. [DOI: 10.1002/(sici)1096-9861(19970421)380:4<507::aid-cne7>3.0.co;2-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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36
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Trottier S, Evrard B, Vignal JP, Scarabin JM, Chauvel P. The serotonergic innervation of the cerebral cortex in man and its changes in focal cortical dysplasia. Epilepsy Res 1996; 25:79-106. [PMID: 8884167 DOI: 10.1016/0920-1211(96)00033-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We present the morphology and the laminar distribution of the serotonin (5-hydroxytryptamine, 5-HT) innervation of the cerebral cortex of patients who underwent cortical resection for partial seizures. The limits of the resections were established by stereoelectroencephalography. The 5-HT innervation was mapped by using an antiserum anti-5-HT. Two patients had cryptogenic epilepsies and two others had seizures related to focal cortical dysplasia. 5-HT immunoreactive axons were morphologically heterogeneous and projected diffusely to the cerebral cortex with regional-specific densities. Two types of terminal axon were demonstrated. Type I had large and spherical (intensely immunoreactive) varicosities and was distributed sparsely with a characteristic predominance in the molecular layer. Type II had fine and pleiomorphic varicosities (granular or fusiform) and was distributed through all cortical layers. The distribution of the 5-HT innervation varied according to the different architectonic areas investigated. The granular cortical areas characterized by a highly developed layer IV (primary somatosensory, primary visual and prefrontal cortices) had the highest density of 5-HT-ir fibers distributed from layer I to layer V. The agranular primary motor cortex had the lowest density with fibers preferentially seen in layers I, IIIa and V-VI. The orbital cortex with a poorly defined layer IV had an intermediate density with a laminar repartition predominant in the supragranular layers. In patients with cryptogenic epilepsies, the brain epileptogenic tissue was histologically normal as well as the serotonergic innervation. In contrast, in patients with focal cortical dysplasia, the dysplastic epileptogenic tissue was characterized by a serotonergic hyperinnervation. In agreement with previous data in primates, we give morphological evidence for two morphologically distinct serotonergic subsystems and for regional specific densities in the human cerebral cortex. Moreover, we previously reported an altered pattern of the catecholaminergic innervation in the same dysplasia areas. All these results provide evidence that this development epileptogenic lesion involves several sets of neurons which may contribute to epileptogenic activity.
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Affiliation(s)
- S Trottier
- CJF 90-12 INSERM, CHR Pontchaillou, Rennes, France
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37
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Smiley JF, Goldman-Rakic PS. Serotonergic axons in monkey prefrontal cerebral cortex synapse predominantly on interneurons as demonstrated by serial section electron microscopy. J Comp Neurol 1996; 367:431-43. [PMID: 8698902 DOI: 10.1002/(sici)1096-9861(19960408)367:3<431::aid-cne8>3.0.co;2-6] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Anatomical approaches were used to describe the distribution, appearance, and synaptic interactions of serotonin (5-HT)-immunoreactive axons in monkey prefrontal cortex. A plexus of 5-HT axons was found throughout the gray matter, with an especially high density in layer I and a slight increase in layer IV. They were strikingly heterogeneous, with a gradient of morphologies ranging from fine and nonvaricose to highly varicose or thick and nonvaricose. Electron microscopy showed that both varicose and nonvaricose axons were typically filled with clear vesicles and less abundant dense core vesicles. A serial section analysis of 5-HT varicosities in layers I, III, and V showed consistent results across layers. Only about 23% of labeled varicosities formed identifiable synapses. These synapses were consistently asymmetric and were 2-5 serial sections (or 0.08-0.38 mu) in diameter. Targets of identified 5-HT synapses were dendritic shafts with the exception of one cell soma. Followed in serial sections, postsynaptic dendrites typically had morphological features of interneurons, i.e. they lacked spines, had a high density of synaptic inputs, and often had a varicose morphology. Only 8% of postsynaptic shafts were classified as pyramidal dendrites. This is in striking contrast to our previous study in this cortex of dopamine axons, which synapsed predominantly on pyramidal dendrites. These are the first results to indicate that interneurons are the major recipient of identifiable 5-HT synapses in the monkey prefrontal cortex.
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Affiliation(s)
- J F Smiley
- Section of Neurobiology, Yale School of Medicine, New Haven, Connecticut 06510 USA
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McQuade R, Sharp T. Release of cerebral 5-hydroxytryptamine evoked by electrical stimulation of the dorsal and median raphe nuclei: effect of a neurotoxic amphetamine. Neuroscience 1995; 68:1079-88. [PMID: 8544983 DOI: 10.1016/0306-4522(95)00214-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Recent neuroanatomical data suggest that the axons and terminals of serotonergic neurons of the dorsal and median raphe nuclei are morphologically and pharmacologically distinct. Here we attempted to establish a functional in vivo model of serotonergic terminals derived from these nuclei, and then carry out a preliminary comparison of their physiological and pharmacological properties. Brain microdialysis was used to monitor extracellular 5-hydroxytryptamine in the hippocampus (dorsal and median raphe innervation) and frontal cortex (preferential dorsal raphe innervation) of the anaesthetized rat. To distinguish 5-hydroxytryptamine released by terminals of dorsal raphe neurons from that released by median raphe neurons, one or other of these nuclei was stimulated electrically. Electrical stimulation of either the dorsal or median raphe nucleus evoked a release of 5-hydroxytryptamine in the hippocampus. Whereas stimulation of the dorsal raphe nucleus also released 5-hydroxytryptamine in the frontal cortex, stimulation of the median raphe nucleus did not. No release of 5-hydroxytryptamine was evoked when electrodes were located in regions bordering the dorsal raphe nucleus and the median raphe nucleus. The amounts of hippocampal 5-HT released by stimulation of the dorsal or median raphe nucleus were found to be similarly altered by a 5-hydroxytryptamine uptake inhibitor (citalopram) and calcium-free perfusion medium, and also by increasing stimulation frequency (2-10 Hz). Furthermore, the amount of 5-hydroxytryptamine released by electrical stimulation of either the dorsal raphe nucleus or median raphe nucleus was markedly reduced in rats pretreated with p-chloroamphetamine. In summary, our data show that electrical stimulation of the dorsal or median raphe nucleus releases 5-hydroxytryptamine in a regionally specific manner (hippocampus versus frontal cortex), suggesting that serotonergic nerve terminals of the dorsal and median raphe pathways were being activated selectively. Using this model, we found no differences in the responsiveness of dorsal and median raphe pathways to a specific set of physiological and pharmacological manipulations. In particular, our data suggest that the neurotoxic action of p-chloroamphetamine may not be targeted solely on serotonergic axons and terminals of the dorsal raphe nucleus but includes those of the median raphe nucleus.
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Affiliation(s)
- R McQuade
- University Department of Clinical Pharmacology, Radcliffe Infirmary, Oxford, U.K
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39
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Winer JA, Larue DT, Pollak GD. GABA and glycine in the central auditory system of the mustache bat: structural substrates for inhibitory neuronal organization. J Comp Neurol 1995; 355:317-53. [PMID: 7636017 DOI: 10.1002/cne.903550302] [Citation(s) in RCA: 135] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The distribution and morphology of neurons and axonal endings (puncta) immunostained with antibodies to gamma-aminobutyric acid (GABA) and glycine (Gly) were analyzed in auditory brainstem, thalamic, and cortical centers in the mustache bat. The goals of the study were (1) to compare and contrast the location of GABAergic and glycinergic neurons and puncta, (2) to determine whether nuclei containing immunoreactive neurons likewise have a similar concentration of puncta, (3) to assess the uniformity of immunostaining within a nucleus and to consider regional differences that were related to or independent of cytoarchitecture, and (4) to compare the patterns recognized in this bat with those in other mammals. There are nine major conclusions. (1) Glycinergic immunostaining is most pronounced in the hindbrain. (2) In the forebrain, GABA alone is present. (3) Some nuclei have GABAergic or glycinergic neurons exclusively; a few have neither. (4) Although there is sometimes a close relationship between the relative number of immunopositive neurons and the density of the puncta, just as often there is no particular correlation between them; this reflects the fact that many GABAergic and glycinergic neurons project beyond their nucleus of origin. (5) Even nuclei devoid of or with few GABAergic or glycinergic neurons contain relatively abundant numbers of puncta; some neurons receive axosomatic terminals of each type. (6) In a few nuclei there are physiological subregions with specific local patterns of immunostaining. (7) The patterns of immunostaining resemble those in other mammals; the principal exceptions are in nuclei that, in the bat, are hypertrophied (such as those of the lateral lemniscus) and in the medial geniculate body. (8) Cellular colocalization of GABA and Gly is specific to only a few nuclei. (9) GABA and glutamic acid decarboxylase (GAD) immunostaining have virtually identical distributions in each nucleus. Several implications follow. First, the arrangements of GABA and Gly in the central auditory system represent all possible patterns, ranging from mutually exclusive to overlapping within a nucleus to convergence of both types of synaptic endings on single neurons. Second, although both transmitters are present in the hindbrain, glycine appears to be dominant, and it is often associated with circuitry in which precise temporal control of aspects of neuronal discharge is critical. Third, the auditory system, especially at or below the level of the midbrain, contains significant numbers of GABAergic or glycinergic projection neurons. The latter feature distinguishes it from the central visual and somatic sensory pathways.
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Affiliation(s)
- J A Winer
- Department of Molecular and Cell Biology, University of California at Berkeley 94720-3200, USA
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40
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Thompson AM, Moore KR, Thompson GC. Distribution and origin of serotoninergic afferents to guinea pig cochlear nucleus. J Comp Neurol 1995; 351:104-16. [PMID: 7534772 DOI: 10.1002/cne.903510110] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The distribution of serotoninergic fibers in the guinea pig cochlear nucleus was studied with serotonin immunohistochemistry. In addition, the origin of the serotoninergic fibers was determined by combining the retrograde transport of wheat germ agglutinin-apohorseradish peroxidase (gold conjugated) with serotonin immunohistochemistry. Immunoreactivity was present in varicose and nonvaricose fibers that were unevenly distributed throughout the cochlear nucleus. The fibers were most prominent in the superficial layers of the dorsal cochlear nucleus and the anterior spherical cell area of the anteroventral cochlear nucleus. Although less prominent, serotonin-positive fibers were also present in the remaining part of the anteroventral cochlear nucleus and the posteroventral cochlear nucleus. A few positive fibers were present in the auditory nerve root and the dorsal and intermediate acoustic striae. Double-labeled cells were found throughout the rostral-caudal extent of the serotoninergic system from the caudal linear nucleus to the nucleus raphe pallidus. However, most were confined to the dorsal (52%) and median (18%) raphe nuclei. Some serotoninergic cell groups contained retrogradely labeled cells that were not serotonin immunoreactive, indicating nonauditory afferents to cochlear nucleus containing other neurotransmitter substances. Serotonin may tonically modulate auditory processing within the cochlear nucleus as well as influence certain ascending auditory pathways. Most of the serotonin in the cochlear nucleus comes from superior raphe nuclei that also project to basal ganglia motor systems and limbic structures. Therefore, the effect of serotonin on the cochlear nucleus may be related to level of arousal or behavioral state.
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Affiliation(s)
- A M Thompson
- Department of Otorhinolaryngology, University of Oklahoma Health Sciences Center, Oklahoma City 73190
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41
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Ascending Noradrenergic and Serotonergic Systems in the Human Brainstem. ADVANCES IN BEHAVIORAL BIOLOGY 1995. [DOI: 10.1007/978-1-4615-1853-2_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Prieto JJ, Peterson BA, Winer JA. Laminar distribution and neuronal targets of GABAergic axon terminals in cat primary auditory cortex (AI). J Comp Neurol 1994; 344:383-402. [PMID: 8063959 DOI: 10.1002/cne.903440305] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The form, density, and neuronal targets of presumptive axon terminals (puncta) that were immunoreactive for gamma-aminobutyric acid (GABA) or its synthesizing enzyme, glutamic acid decarboxylase (GAD), were studied in cat primary auditory cortex (AI) in the light microscope. High-resolution, plastic-embedded material and frozen sections were used. The chief results were: 1) There was a three-tiered numerical distribution of puncta, with the highest density in layer Ia, an intermediate number in layers Ib-IVb, and the lowest concentration in layers V and VI, respectively. 2) Each layer had a particular arrangement: layer I puncta were fine and granular (less than 1 micron in diameter), endings in layers II-IV were coarser and more globular (larger than 1 micron), and layer V and VI puncta were mixed in size and predominantly small. 3) The form and density of puncta in every layer were distinctive. 4) Immunonegative neurons received, in general, many more axosomatic puncta than immunopositive cells, with the exception of the large multipolar (presumptive basket) cells, which invariably had many puncta in layers II-VI. 5) The number of puncta on the perikarya of GABAergic neurons was sometimes related to the number of puncta in the layer, and in other instances it was independent of the layer. Thus, while layer V had a proportion of GABAergic neurons similar to layer IV, it had only a fraction of the number of puncta; perhaps the intrinsic projections of supragranular GABAergic cells are directed toward layer IV, as those of infragranular GABAergic neurons may be. Since puncta are believed to be the light microscopic correlate of synaptic terminals, they can suggest how inhibitory circuits are organized. Even within an area, the laminar puncta patterns may reflect different inhibitory arrangements. Thus, in layer I the fine, granular endings could contact preferentially the distal dendrites of pyramidal cells in deeper layers. The remoteness of such terminals from the spike initiation zone contrasts with the many puncta on all pyramidal cell perikarya and the large globular endings on basket cell somata. Basket cells might receive feed-forward disinhibition, pyramidal cells feed-forward inhibition, and GABAergic non-basket cells would be the target of only sparse inhibitory axosomatic input. Such arrangements imply that the actions of GABA on AI neurons are neither singular nor simple and that the architectonic locus, laminar position, and morphological identity of a particular neuron must be integrated for a more refined view of its role in cortical circuitry.
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Affiliation(s)
- J J Prieto
- Department of Molecular and Cell Biology, University of California, Berkeley 94720-2097
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43
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Abstract
Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry was used to study the morphology of labeled axonal plexuses in the human lateral temporal cortex. Strongly stained non-pyramidal neurons and a dense NADPH diaphorase-positive network of fibers were observed in all cortical layers. Certain stained fibers are found to give rise to basket-like formations. Notably other fibers seem to innervate small blood vessels. In addition, numerous blood vessels show a punctate labeling over their surfaces. These findings provide new morphological and chemical details of the axonal innervation of the human neocortex.
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44
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Rahman S, Neuman RS. Activation of 5-HT2 receptors facilitates depolarization of neocortical neurons by N-methyl-D-aspartate. Eur J Pharmacol 1993; 231:347-54. [PMID: 8449227 DOI: 10.1016/0014-2999(93)90109-u] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The interaction between serotonin and excitatory amino acid agonists at rat neocortical neurons was investigated using the grease-gap recording method. Depolarization evoked by 50 microM N-methyl-D-aspartate was dose dependently facilitated by serotonin (5-HT) (1 to 100 microM) giving a bell-shaped dose-response curve with maximum enhancement at 30 microM. In contrast, quisqualate and kainate depolarizations were not enhanced. Subnanomolar concentrations of methysergide, ritanserin and spiperone, but not ICS 205-930, attenuated the 5-HT enhancement, compatible with 5-HT2, but not 5-HT1 or 5-HT3 receptor subtype involvement. Enhancement was observed with 5-HT2 receptor agonists, whereas 5-HT1 receptor subtype agonists had either no effect (1B and 1C) or reduced (1A) the N-methyl-D-aspartate depolarization. Scopolamine and prazosin reduced the N-methyl-D-aspartate depolarization and blocked facilitation induced by carbachol and phenylephrine, but not that due to 5-HT. Tetrodotoxin reduced the N-methyl-D-aspartate depolarization, but the facilitation by 5-HT persisted. Activators of protein kinase C (phorbol diacetate and 1-oleoyl-2-acetyl-sn-glycerol) did not mimic the serotonin facilitation. We conclude that serotonin enhances N-methyl-D-aspartate depolarization of rat cortical neurons through activation of 5-HT2 receptors, however the cellular mechanism underlying the facilitation remains to be established.
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Affiliation(s)
- S Rahman
- Faculty of Medicine, Memorial University, St. John's Newfoundland, Canada
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45
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Mathiau P, Riche D, Behzadi G, Dimitriadou V, Aubineau P. Absence of serotonergic innervation from raphe nuclei in rat cerebral blood vessels--I. Histological evidence. Neuroscience 1993; 52:645-55. [PMID: 7680791 DOI: 10.1016/0306-4522(93)90413-a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Anterograde tracing from dorsal raphe neurons by Phaseolus vulgaris leucoagglutinin and serotonin immunocytochemistry revealed no serotonergic projections from raphe nuclei to cerebral pial vessels in the rat. However, cerebrovascular nerve fibres, mainly located in major pial arteries, were immunoreactive to tryptophan-5-hydroxylase antibodies as previously shown by others. It thus seems that the rate-limiting enzyme catalysing the biosynthesis of serotonin, tryptophan-5-hydroxylase, is present in cerebrovascular nerve fibres which do not originate in the dorsal raphe nucleus and which do not contain enough serotonin to be labelled by serotonin immunocytochemistry. We also observed tryptophan hydroxylase-immunoreactive but no serotonin-immunoreactive nerve fibres in the femoral artery and, occasionally, in the dura mater. The femoral artery, like the dura mater, contained numerous mast cells reacting positively to both tryptophan hydroxylase and to serotonin immunocytochemistry. The colocalization of the enzyme and its final product thus appears to be a general feature, since it has already been demonstrated within the central nervous system. The only exception appears to be the tryptophan hydroxylase-immunoreactive nerves present in cerebral and peripheral vessels. These results suggest that there is not a true serotonergic (i.e. serotonin-containing) innervation in cerebral blood vessels. They also strongly suggest that the cerebrovascular nerve fibres which appear to contain tryptophan hydroxylase do not originate in the raphe nuclei.
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Affiliation(s)
- P Mathiau
- Laboratoire de Recherches Cérébrovasculaires, CNRS U.A.641, Paris, France
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46
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McCormick DA. Neurotransmitter actions in the thalamus and cerebral cortex and their role in neuromodulation of thalamocortical activity. Prog Neurobiol 1992; 39:337-88. [PMID: 1354387 DOI: 10.1016/0301-0082(92)90012-4] [Citation(s) in RCA: 828] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- D A McCormick
- Section of Neurobiology, Yale University School of Medicine, New Haven, CT 06510
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47
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Smiley JF, Williams SM, Szigeti K, Goldman-Rakic PS. Light and electron microscopic characterization of dopamine-immunoreactive axons in human cerebral cortex. J Comp Neurol 1992; 321:325-35. [PMID: 1506472 DOI: 10.1002/cne.903210302] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The distribution and synaptic connections of dopamine axons were studied by light and electron microscopy in human cerebral cortex. For this purpose, dopamine immunoreactivity was characterized in apparently normal anteriolateral temporal cortex, which was removed to gain access to the medial temporal lobe during tumor excision or treatment of epilepsy. Nissl sections showed this to be granular neocortex. Dopamine fibers were distributed throughout this cortex, although there were relatively more fibers in layers I-II and in layers V-VIa, compared to layers III-IV and VIb, resulting in a bilaminar pattern of labeling. In all layers, fibers were seen to form numerous varicosities, and to vary in size from thick to very fine. Fibers were relatively straight, sparsely branched and were oriented in various planes within the cortex. However, in layer I, they often ran parallel to the pial surface. In order to analyze the functional interactions of dopamine fibers, individual cortical layers were surveyed for dopamine synapses. These were usually symmetrical (Gray's type II), although 13% of them were asymmetrical. Approximately 60% of dopamine synapses were made with dendritic spines, and 40% with dendritic shafts, and this ratio was similar in all layers. On both spines and shafts, it was common to see dopamine synapses closely apposed to an unlabeled asymmetric input, suggesting a dopamine modulation of excitatory input. Some postsynaptic dendritic shafts had features of pyramidal cells, including formation of spines. Since pyramidal cells are the major type of cortical spiny neuron, they probably represent the main target of dopamine synapses in this cortex. There were also dopamine profiles apposed to membrane densities on unlabeled axon terminals, suggesting another type of synaptic interaction. These findings provide the first documentation of dopamine synapses in the human cortex, and show that they form classical synaptic junctions. The location of these synapses on spines and distal dendrites, and their proximity to asymmetric synapses, suggest a modulatory role on excitatory input to pyramidal cells.
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Affiliation(s)
- J F Smiley
- Section of Neurobiology, Yale School of Medicine, New Haven, Connecticut 06510
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48
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Hornung JP, Celio MR. The selective innervation by serotoninergic axons of calbindin-containing interneurons in the neocortex and hippocampus of the marmoset. J Comp Neurol 1992; 320:457-67. [PMID: 1629398 DOI: 10.1002/cne.903200404] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The serotoninergic input to the mammalian cerebral cortex originates in the median and the dorsal raphe nuclei. Median raphe neurons have been previously shown to give rise to beaded varicose axons which form dense pericellular arrays (baskets) surrounding the soma and the proximal dendrites of certain cortical neurons. In the present study, we have searched for specific markers characterizing the neurons of the marmoset neocortex and hippocampus surrounded by these thick varicose serotonin-containing fibers. The non-pyramidal nature of these neurons, suggested by their dendritic arborization, was correlated, in immunocytochemical experiments with double-labelling to demonstrate their surrounding serotonin-containing basket and their content of glutamic acid decarboxylase (GAD) or of the calcium-binding protein calbindin. Another calcium-binding protein common in numerous non-pyramidal cortical neurons, parvalbumin, was never found in neurons surrounded by serotonin-containing baskets. This organization was found in all areas of the neocortex and of the hippocampus where serotonin-containing baskets were present. One of the serotoninergic cortical inputs which originates from the brainstem tegmentum, traditionally described as "diffuse," proves to be highly selective in that a subset of its axons terminates preferentially on a subpopulation of inhibitory interneurons of the cerebral cortex. It may be emphasized that this subset of cortical interneurons has now been shown to be characterized not only by its axonal and dendritic arborization and its neurotransmitter, but also by a specific type of input which can modulate cortical function in a unique manner.
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Affiliation(s)
- J P Hornung
- Institute of Anatomy, Faculty of Medicine, University of Lausanne, Switzerland
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49
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Vu DH, Törk I. Differential development of the dual serotoninergic fiber system in the cerebral cortex of the cat. J Comp Neurol 1992; 317:156-74. [PMID: 1573061 DOI: 10.1002/cne.903170205] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The changes in distribution and density of the serotoninergic innervation of the cerebral cortex were studied in kittens from birth (PO) to 60 days of age (P59). Three cortical areas were sampled: prefrontal, primary auditory, and primary visual areas. Two systems of serotoninergic axons were demonstrated by immunocytochemical techniques: the fine axon system characterized by small fusiform varicosities up to 1 micron in diameter, and the beaded axon system, the fibers of which have round varicosities up to 5 microns in diameter. The density of the two types of fibers across the cortical layers at different ages was measured with a semiautomatic computerized system. In all three areas, the density of fine axons increased steadily from birth, although the pattern of innervation changed from an even distribution at PO to a distinct concentration of the fibers in layers I-III by week 2 in the prefrontal cortex and by week 3 in auditory and visual cortices. By contrast, the beaded axons first appeared in the cortex at week 2 for the prefrontal cortex, at week 3 in auditory and visual areas. Initially, these fibers were distributed throughout all cortical layers and were of much lower density than the fine axons. At later ages the beaded axons became confined to layers I-III where they gradually increased in number, and from week 4, they formed pericellular arrays which were only observed in the prefrontal and auditory cortices, not in visual cortex. These findings provide further evidence for the existence of two parallel subsystems of serotoninergic axons which are different not only in their morphology and nuclear origin, but also in their development. Our finding that the two serotoninergic fiber systems arrive in the cortex in two different stages suggests that they have differential roles in development. The late formation of the pericellular arrays indicates that the formation of the specific connections made by the beaded fibers could be dependent on a certain degree of maturity of the target neurons.
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Affiliation(s)
- D H Vu
- School of Anatomy, University of New South Wales, Kensington, Sydney, Australia
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50
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Lolova I, Davidoff M. Age-related changes in serotonin-immunoreactive neurons in the rat nucleus raphe dorsalis and nucleus centralis superior: a light microscope study. Mech Ageing Dev 1992; 62:279-89. [PMID: 1583913 DOI: 10.1016/0047-6374(92)90113-r] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Comparison of serotonin-immunoreactive (SER-IR) neurons in the nucleus raphe dorsalis (NRD) and the nucleus centralis superior (NCS) of 3-month-old and 28-month-old rats was made using qualitative and quantitative immunohistochemical analysis. Significant age-related changes in size and density of the SER-IR somata as well as in the length and number of their processes were demonstrated. A different vulnerability of the SER-IR neurons in both raphe nuclei to aging was observed that may be related to their different structural and functional features.
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Affiliation(s)
- I Lolova
- Institute of Physiology, Bulgarian Academy of Sciences, Sofia
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