Serotonergic Suppression of Interhemispheric Cortical Synaptic Potentials

Brain Res. 1994 Apr 18;643(1-2):17-28. doi: 10.1016/0006-8993(94)90004-3.

Abstract

The inhibitory effects of 5-hydroxytryptamine (5-HT) on interhemispheric and intracortical synaptic potentials in layer V neurons of the rat medial prefrontal (MFC) cortex were examined. Low concentrations (1-3 microM) of 5-HT selectively attenuated polysynaptic potentials that were similarly evoked by callosal or white matter stimulation. Maximally effective concentrations of 5-HT blocked interhemispheric transmission by 50-90%, as evidenced by an attention of the short latency callosal depolarizing synaptic potential (e-DPSP). These effects of 5-HT were not associated with a change in membrane potential or input resistance. The e-DPSP was characterized as having an N-methyl-D-aspartate (NMDA) and a non-NMDA component; the non-NMDA component was attenuated by 5-HT. Attenuation of the synaptic potential was accompanied by an attenuation of a postsynaptic glutamate potential. Suppression of both the e-DPSP and the glutamate potential was concentration dependent with 10-100 microM being maximally effective. The 5-HT1A/2 antagonist, spiperone, antagonized the effects of 5-HT on synaptic and glutamate potentials. Spiperone (1 microM) shifted the concentration-effect curves for suppression of the e-DPSP and the glutamate potential to the right; however, the Kb for the glutamate potential concentration-effect curve was 10 times that for the e-DPSP curve. The differential antagonist sensitivity of synaptic and glutamate potentials was an indication that serotonin acted on more than one receptor subtype to reduce interhemispheric transmission.

MeSH terms

  • 2-Amino-5-phosphonovalerate / pharmacology
  • Animals
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / physiology*
  • Corpus Callosum / physiology*
  • Dose-Response Relationship, Drug
  • Electric Stimulation
  • Evoked Potentials / drug effects
  • Functional Laterality
  • Glutamates / pharmacology
  • Glutamic Acid
  • In Vitro Techniques
  • Male
  • Membrane Potentials / drug effects*
  • Neurons / drug effects
  • Neurons / physiology*
  • Prefrontal Cortex / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / pharmacology*
  • Spiperone / pharmacology
  • Synaptic Transmission / drug effects*
  • Time Factors

Substances

  • Glutamates
  • Serotonin
  • Glutamic Acid
  • Spiperone
  • 2-Amino-5-phosphonovalerate