A major role for thalamocortical afferents in serotonergic hallucinogen receptor function in the rat neocortex

Neuroscience. 2001;105(2):379-92. doi: 10.1016/s0306-4522(01)00199-3.

Abstract

Activation of 5-hydroxytryptamine(2A) (5-HT(2A)) receptors by hallucinogenic drugs is thought to mediate many psychotomimetic effects including changes in affect, cognition and perception. Conversely, blockade of 5-HT(2A) receptors may mediate therapeutic effects of many atypical antidepressant and antipsychotic drugs. The purpose of the present study was to determine the source of subcortical glutamatergic afferents, which would project widely throughout the anterior-posterior axis of the rat brain to the apical dendrites of layer V pyramidal cells of the medial prefrontal cortex, from which serotonin induces transmitter release via activation of 5-HT(2A) receptors. Fiber-sparing chemical lesions of the medial thalamus selectively decreased the frequency of serotonin-induced excitatory postsynaptic currents recorded from layer V pyramidal cells in the prelimbic region of the medial prefrontal cortex by 60%. In contrast, large bilateral lesions of the amygdala did not alter the serotonin response. These thalamic lesions significantly decreased the amount of binding to either mu-opioid or metabotropic glutamate 2/3 receptors in the prelimbic region of the medial prefrontal cortex as expected from previous evidence that these agonists for these receptors suppress serotonin-induced excitatory postsynaptic currents by a presynaptic mechanism. Surprisingly, the amount of specific binding to cortical 5-HT(2A) receptors was significantly increased by the medial thalamic lesions. Thus, these experiments demonstrate that activation of cortical 5-HT(2A) receptors modulates transmitter release from thalamocortical terminals. Unexpectedly, lesioning the thalamocortical terminals also alters 5-HT(2A) receptor binding in the prefrontal cortex. These findings are of interest with respect to understanding therapeutic effects of antidepressant/antipsychotic drugs and the known behavioral effects of thalamic lesions in humans.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amygdala / cytology
  • Amygdala / drug effects
  • Amygdala / metabolism
  • Animals
  • Bridged Bicyclo Compounds / pharmacology
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Hallucinogens / pharmacology*
  • Male
  • N-Methylaspartate / pharmacology
  • Neural Pathways / cytology
  • Neural Pathways / drug effects
  • Neural Pathways / metabolism*
  • Prefrontal Cortex / cytology
  • Prefrontal Cortex / drug effects
  • Prefrontal Cortex / metabolism*
  • Pyramidal Cells / cytology
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / metabolism
  • Radioligand Assay
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Serotonin, 5-HT2A
  • Receptors, Metabotropic Glutamate / drug effects
  • Receptors, Metabotropic Glutamate / metabolism
  • Receptors, Opioid, mu / drug effects
  • Receptors, Opioid, mu / metabolism
  • Receptors, Serotonin / drug effects
  • Receptors, Serotonin / metabolism*
  • Serotonin / metabolism*
  • Serotonin / pharmacology
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology*
  • Thalamus / cytology
  • Thalamus / drug effects
  • Thalamus / metabolism*
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology

Substances

  • Bridged Bicyclo Compounds
  • Excitatory Amino Acid Agonists
  • Hallucinogens
  • Receptor, Serotonin, 5-HT2A
  • Receptors, Metabotropic Glutamate
  • Receptors, Opioid, mu
  • Receptors, Serotonin
  • metabotropic glutamate receptor 2
  • Serotonin
  • N-Methylaspartate
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
  • eglumetad