Research report
Distribution of the serotonin 5-HT2 receptor family mRNAs: comparison between 5-HT2A and 5-HT2C receptors

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Abstract

Because of their similarities, serotonin 5-HT2, 5-HT1C, and the recently described 5-HT2F receptors have been classified as members of the 5-HT2 receptor family, and they have been renamed 5-HT2A, 5-HT2C and 5-HT2B, respectively. The regional distribution and cellular localization of mRNA coding for the members of 5-HT2 receptor family were investigated in consecutive tissue sections from the rat brain by in situ hybridization histochemistry. No evidence for the expression of 5-HT2B receptor was found. High levels of 5-HT2A (formerly 5-HT2) receptor mRNA were observed only in few areas, as the frontal cortex, piriform cortex, ventro-caudal part of CA3, medial mammilary nucleus, the pontine nuclei and the motor cranial nerve nuclei in the brainstem, and the ventral horn of the spinal cord. The distribution of 5-HT2A receptor mRNA is generally in good agreement with that of the corresponding binding sites, although discrepancies were sometimes observed. 5-HT2C (formerly 5-HT1C) mRNA was present at very high levels in the choroid plexuses. However, very high levels were also seen in many other brain regions, as the retrosplenial, piriform and entorhinal cortex, anterior olfactory nucleus, lateral septal nucleus, subthalamic nucleus, amygdala, subiculum and ventral part of CA3, lateral habenula, substantia nigra pars compacta, several brainstem nuclei and the whole grey matter of the spinal cord. These results confirm and extend previous observations that 5-HT2C receptor mRNA is present in many brain areas in addition to those autoradiographically shown to have the corresponding binding sites and that 5-HT2C receptor subtype is a principal 5-HT receptor in the brain. From the comparison between their distributions, 5-HT2A and 5-HT2C receptor mRNAs appeared to be expressed in distinct but overlapping sets of brain regions. Both mRNAs coexisted at high levels in the anterior olfactory nucleus, piriform cortex, endopiriform nucleus, claustrum, pyramidal cell layer of the ventral part of CA3, taenia tecta, substantia nigra pars compacta, and several brainstem nuclei. In other regions both mRNAs were present but with different distributions, as the caudate-putamen. These results are also discussed in relation to the physiological meaning of the existence of two so similar receptor subtypes in the brain.

References (38)

  • P.W. Sheldon et al.

    Serotonin (5-HT) induces IPSPs in pyramidal layer cells of rat piriform cortex: evidence for involvement of a 5-HT2-activated interneuron

    Brain Res.

    (1990)
  • S.R. White et al.

    Serotonin depolarizes cat spinal motoneurons in situ and decreases motoneurons after-hyperpolarization potentials

    Brain Res.

    (1989)
  • N.M. Appel et al.

    Autoradiographic characterization of (±)-1-(2,5-dimethoxy-4-[125I]iodophenyl)-2-aminopropane ([125I]DOI) binding to 5-HT2 and 5-HT1C receptors in rat brain

    J. Pharmacol. Exp. Ther.

    (1990)
  • Conn, P.J. and Sanders-Bush, E., Agonist-induced phosphoinositide hydrolysis in choroid plexus, J. Neurochem., 47...
  • C.C. Felder et al.

    Serotonin stimulates phospholipase A2 and the release of arachidonic acid in hippocampal neurons by a type 2 serotonin receptor that is independent of inisitolphospholipid hydrolysis

  • M. Foguet et al.

    Cloning and functional characterization of the rat stomach fundus serotonin receptor

    EMBO J.

    (1992)
  • M. Foguet et al.

    Structure of the mouse 5-HT1C, 5-HT2 and stomach fundus serotonin receptor genes

    NeuroReport

    (1992)
  • L.B. Haberly

    Structure of the piriform cortex of the opossum. I. Description of neuron types with Golgi methods

    J. Comp. Neurol.

    (1983)
  • M.M. Hosey

    Diversity of structure, signaling and regulation within the family of muscarinic cholinergic receptors

    FASEB J.

    (1992)
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