Potentiation of excitatory serotonergic responses by MK-801 in the medial prefrontal cortex

Naunyn Schmiedebergs Arch Pharmacol. 2009 Nov;380(5):383-97. doi: 10.1007/s00210-009-0446-4.


New atypical antipsychotics show a greater affinity to serotonergic rather than to dopamine receptors, suggesting that serotonin (5-HT) has a major role in the pathophysiology and treatment of schizophrenia. The goal of this study was to characterise the response of pyramidal neurons in the medial prefrontal cortex (mPFC) to 5-HT and NMDA before and after administration of the NMDA receptor antagonist, MK-801 (dizocilpine), a well-validated pharmacological model of psychosis. mPFC pyramidal (glutamatergic) neurons were recorded in urethane-anaesthetised rats. The responses to NMDA and 5-HT were assessed using in vivo electrophysiology and microiontophoresis. The 5-HT2A/2C antagonist ritanserin and the 5-HT1A antagonist WAY100635 were used to block 5-HT responses. MK-801 decreased the NMDA-induced excitatory responses and increased NMDA-evoked burst activity among mPFC pyramidal neurons. Three subpopulations of pyramidal cells were identified according to their responses to 5-HT: excitation (33%), inhibition (40%) and non-response (27%). The inhibitory responses were blocked by WAY100635 in 100% of cases, but not by ritanserin; the excitatory responses were blocked by ritanserin in 75% of cases, but not by WAY100635. The administration of MK-801 potentiated the firing rate of excitatory responses but did not modify the inhibitory responses induced by microiontophoretic application of 5-HT. These results suggest that MK-801 modifies 5-HT synapses in the mPFC by potentiating the excitatory 5-HT2A/2C responses and attenuating NMDA excitations. These data indicate that 5-HT excitatory transmission is selectively impaired at the mPFC level in this pharmacological model of schizophrenia.

MeSH terms

  • Animals
  • Disease Models, Animal
  • Dizocilpine Maleate / pharmacology*
  • Electrophysiology
  • Excitatory Amino Acid Antagonists / pharmacology*
  • Iontophoresis / methods
  • Male
  • N-Methylaspartate / metabolism
  • Prefrontal Cortex / drug effects
  • Prefrontal Cortex / metabolism
  • Pyramidal Cells / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Serotonin, 5-HT2A / drug effects
  • Receptor, Serotonin, 5-HT2A / metabolism
  • Receptor, Serotonin, 5-HT2C / drug effects
  • Receptor, Serotonin, 5-HT2C / metabolism
  • Schizophrenia / physiopathology*
  • Serotonin / metabolism*
  • Synaptic Transmission / drug effects


  • Excitatory Amino Acid Antagonists
  • Receptor, Serotonin, 5-HT2A
  • Receptor, Serotonin, 5-HT2C
  • Serotonin
  • N-Methylaspartate
  • Dizocilpine Maleate