The Accounting Review

Serotonin receptors of the 5-HT2A subtype are robustly expressed in the cerebral cortex where they have been implicated in the pathophysiology and therapeutics of mental disorders and the actions of hallucinogens. Much less is known, however, about the specific cell types expressing 5-HT2A receptors in cortex. In the current study we use immunohistochemical and electrophysiological approaches in genetically modified mice to address the expression of the Htr2a gene and 5-HT2A receptors in cortex. We first use an EGFP-expressing BAC transgenic mice and identify three main Htr2A gene expressing neuronal populations in cortex. The largest of these cell populations corresponds to layer V pyramidal cells of the anterior cortex, followed by GABAergic interneurons of the middle layers, and non-pyramidal cells of the subplate/Layer VIb. We then use 5-HT2A receptor knockout mice to identify an antibody capable of localizing 5-HT2A receptors in brain and use it to map these receptors. We find strong laminar expression of 5-HT2A receptors in cortex, especially along a diffuse band overlaying layer Va. This band exhibits a strong anteroposterior gradient that closely matches the localization of Htr2A expressing pyramidal cells of layer V. Finally we use electrophysiological and immunohistochemical approaches to show that most, but not all, GABAergic interneurons of the middle layers are parvalbumin expressing Fast-spiking interneurons and that these cells are depolarized and excited by serotonin, most likely through the activation of 5-HT2A receptors. These results clarify and extend our understanding of the cellular distribution of 5-HT2A receptors in the cerebral cortex.

[1]  F. Zhou,et al.  Activation of serotonin receptors modulates synaptic transmission in rat cerebral cortex. , 1999, Journal of neurophysiology.

[2]  P P Humphrey,et al.  International Union of Pharmacology classification of receptors for 5-hydroxytryptamine (Serotonin). , 1994, Pharmacological reviews.

[3]  G. Kinney,et al.  Serotonergic Modulation of Supragranular Neurons in Rat Sensorimotor Cortex , 2002, The Journal of Neuroscience.

[4]  D. Morilak,et al.  Immunocytochemical localization and description of neurons expressing serotonin2 receptors in the rat brain , 1993, Neuroscience.

[5]  N. Heintz,et al.  Bac to the future: The use of bac transgenic mice for neuroscience research , 2001, Nature Reviews Neuroscience.

[6]  J. Palacios,et al.  Quantitative autoradiographic mapping of serotonin receptors in the rat brain. I. Serotonin-1 receptors , 1985, Brain Research.

[7]  M. Pompeiano,et al.  Distribution of the serotonin 5-HT2 receptor family mRNAs: comparison between 5-HT2A and 5-HT2C receptors. , 1994, Brain research. Molecular brain research.

[8]  D. Morilak,et al.  Developmental regulation of 5-HT2 and 5-HT1c receptor gene expression in rat brain. , 1993, Psychopharmacology series.

[9]  S. Grant,et al.  PSD-95 Is Essential for Hallucinogen and Atypical Antipsychotic Drug Actions at Serotonin Receptors , 2009, The Journal of Neuroscience.

[10]  J. Palacios,et al.  Mapping of 5‐HT2A receptors and their mRNA in monkey brain: [3H]MDL100,907 autoradiography and in situ hybridization studies , 2001, The Journal of comparative neurology.

[11]  P S Goldman-Rakic,et al.  5-Hydroxytryptamine2A serotonin receptors in the primate cerebral cortex: possible site of action of hallucinogenic and antipsychotic drugs in pyramidal cell apical dendrites. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[12]  B. Roth,et al.  Control of Serotonergic Function in Medial Prefrontal Cortex by Serotonin-2A Receptors through a Glutamate-Dependent Mechanism , 2001, The Journal of Neuroscience.

[13]  J. Palacios,et al.  Quantitative autoradiographic mapping of serotonin receptors in the rat brain. II. Serotonin-2 receptors , 1985, Brain Research.

[14]  F. Mascagni,et al.  Neuronal localization of 5-HT type 2A receptor immunoreactivity in the rat basolateral amygdala , 2007, Neuroscience.

[15]  J. John Mann,et al.  Cortical 5-HT2A Receptor Signaling Modulates Anxiety-Like Behaviors in Mice , 2006, Science.

[16]  J. Palacios,et al.  Serotonin receptors in the human brain. II. Characterization and autoradiographic localization of 5-HT1C and 5-HT2 recognition sites , 1986, Brain Research.

[17]  L. Descarries,et al.  Cellular and subcellular distribution of the serotonin 5‐HT2A receptor in the central nervous system of adult rat , 1999, The Journal of comparative neurology.

[18]  K Fuxe,et al.  Relationships of 5-hydroxytryptamine immunoreactive terminal-like varicosities to 5-hydroxytryptamine-2A receptor-immunoreactive neuronal processes in the rat forebrain , 2001, Journal of Chemical Neuroanatomy.

[19]  Michael Brecht,et al.  Barrel cortex and whisker-mediated behaviors , 2007, Current Opinion in Neurobiology.

[20]  R. Andrade,et al.  Serotonergic regulation of calcium‐activated potassium currents in rodent prefrontal cortex , 2005, The European journal of neuroscience.

[21]  Trevor Sharp,et al.  A review of central 5-HT receptors and their function , 1999, Neuropharmacology.

[22]  R. Andrade,et al.  Mechanism of the 5-hydroxytryptamine 2A receptor-mediated facilitation of synaptic activity in prefrontal cortex , 2007, Proceedings of the National Academy of Sciences.

[23]  R. Andrade,et al.  Serotonergic Regulation of Membrane Potential in Developing Rat Prefrontal Cortex: Coordinated Expression of 5-Hydroxytryptamine (5-HT)1A, 5-HT2A, and 5-HT7 Receptors , 2004, The Journal of Neuroscience.

[24]  D. Vergé,et al.  The 5‐HT2A receptor is widely distributed in the rat spinal cord and mainly localized at the plasma membrane of postsynaptic neurons , 2004, The Journal of comparative neurology.

[25]  R. Andrade,et al.  TRPC Channels Mediate a Muscarinic Receptor-Induced Afterdepolarization in Cerebral Cortex , 2009, The Journal of Neuroscience.

[26]  S. Hamada,et al.  Localization of 5-HT2A receptor in rat cerebral cortex and olfactory system revealed by immunohistochemistry using two antibodies raised in rabbit and chicken. , 1998, Brain research. Molecular brain research.

[27]  Andreas Bäbler,et al.  Psilocybin induces schizophrenia‐like psychosis in humans via a serotonin‐2 agonist action , 1998, Neuroreport.

[28]  B. Gloss,et al.  Drd1a-tdTomato BAC Transgenic Mice for Simultaneous Visualization of Medium Spiny Neurons in the Direct and Indirect Pathways of the Basal Ganglia , 2008, The Journal of Neuroscience.

[29]  R. Andrade,et al.  5-Hydroxytryptamine2 receptor facilitates GABAergic neurotransmission in rat hippocampus. , 1998, The Journal of pharmacology and experimental therapeutics.

[30]  B. Roth,et al.  Localization of 5-HT2A receptors on dopamine cells in subnuclei of the midbrain A10 cell group , 2002, Neuroscience.

[31]  B. Roth,et al.  UC San Francisco UC San Francisco Previously Published Works Title The pipeline and future of drug development in schizophrenia , 2008 .

[32]  A. Deutch,et al.  Serotonin 5‐HT2A receptors are expressed on pyramidal cells and interneurons in the rat cortex , 1997, Synapse.

[33]  R. Reep Cortical Layer VII and Persistent Subplate Cells in Mammalian Brains , 2000, Brain, Behavior and Evolution.

[34]  Y. Kawaguchi,et al.  Serotonin Modulates Fast-Spiking Interneuron and Synchronous Activity in the Rat Prefrontal Cortex through 5-HT1A and 5-HT2A Receptors , 2010, The Journal of Neuroscience.

[35]  G. Aghajanian,et al.  Serotonin Induces Excitatory Postsynaptic Potentials in Apical Dendrites of Neocortical Pyramidal Cells , 1997, Neuropharmacology.

[36]  H. Markram,et al.  Interneurons of the neocortical inhibitory system , 2004, Nature Reviews Neuroscience.

[37]  E. sanders-Bush,et al.  Generation of anti-peptide antibodies against serotonin 5-HT2A and 5-HT2C receptors , 1997, Journal of Neuroscience Methods.

[38]  Gordon M. G. Shepherd,et al.  Intracortical Cartography in an Agranular Area , 2009, Front. Neurosci..

[39]  G. Feng,et al.  Imaging Neuronal Subsets in Transgenic Mice Expressing Multiple Spectral Variants of GFP , 2000, Neuron.

[40]  M. Pompeiano,et al.  Localization of the mRNA for the 5-HT2 receptor by in situ hybridization histochemistry. Correlation with the distribution of receptor sites , 1990, Brain Research.

[41]  Y. Kubota,et al.  GABAergic cell subtypes and their synaptic connections in rat frontal cortex. , 1997, Cerebral cortex.

[42]  J. Palacios,et al.  Selective visualization of rat brain 5-HT2A receptors by autoradiography with [3H]MDL 100,907 , 1997, Naunyn-Schmiedeberg's Archives of Pharmacology.

[43]  J. Yracheta,et al.  Functional chemical neuroanatomy of serotonergic neurons and their targets: antibody production and immunohistochemistry (IHC) for 5-HT, its precursor (5-HTP) and metabolite (5-HIAA), biosynthetic enzyme (TPH), transporter (SERT), and three receptors (5-HT2A, 5-ht5a, 5-HT7). , 1998, Annals of the New York Academy of Sciences.

[44]  S. Sesack,et al.  Ultrastructural localization of serotonin2A receptors in the middle layers of the rat prelimbic prefrontal cortex , 2003, Neuroscience.

[45]  Zhong-wei Zhang Serotonin Induces Tonic Firing in Layer V Pyramidal Neurons of Rat Prefrontal Cortex during Postnatal Development , 2003, The Journal of Neuroscience.

[46]  A. Serretti,et al.  HTR2A gene variants and psychiatric disorders: a review of current literature and selection of SNPs for future studies. , 2007, Current medicinal chemistry.

[47]  Shiaoching Gong,et al.  A gene expression atlas of the central nervous system based on bacterial artificial chromosomes , 2003, Nature.

[48]  Mark Ellisman,et al.  Development and Characterization of Monoclonal Antibodies Specific to the Serotonin 5-HT2A Receptor , 1998, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[49]  M. Molliver,et al.  Correspondence between 5-HT2 receptors and serotonergic axons in rat neocortex , 1988, Brain Research.

[50]  B. Dean The cortical serotonin2A receptor and the pathology of schizophrenia: a likely accomplice , 2003, Journal of neurochemistry.

[51]  P. Jonas,et al.  Synaptic mechanisms of synchronized gamma oscillations in inhibitory interneuron networks , 2007, Nature Reviews Neuroscience.