Activation of serotonin receptors modulates synaptic transmission in rat cerebral cortex.
The cerebral cortex receives an extensive serotonergic (5-hydroxytryptamine, 5-HT) input. Immunohistochemical studies suggest that inhibitory neurons are the main target of 5-HT innervation. In vivo extracellular recordings have shown that 5-HT generally inhibited cortical pyramidal neurons, whereas in vitro studies have shown an excitatory action. To determine the cellular mechanisms underlying the diverse actions of 5-HT in the cortex, we examined its effects on cortical inhibitory interneurons and pyramidal neurons. We found that 5-HT, through activation of 5-HT(2A) receptors, induced a massive enhancement of spontaneous inhibitory postsynaptic currents (sIPSCs) in pyramidal neurons, lasting for approximately 6 min. In interneurons, this 5-HT-induced enhancement of sIPSCs was much weaker. Activation of 5-HT(2A) receptors also increased spontaneous excitatory postsynaptic currents (sEPSCs) in pyramidal neurons. This response desensitized less and at a slower rate. In contrast, 5-HT slightly decreased evoked IPSCs (eIPSCs) and eEPSCs. In addition, 5-HT via 5-HT(3) receptors evoked a large and rapidly desensitizing inward current in a subset of interneurons and induced a transient enhancement of sIPSCs. Our results suggest that 5-HT has widespread effects on both interneurons and pyramidal neurons and that a short pulse of 5-HT is likely to induce inhibition whereas the prolonged presence of 5-HT may result in excitation.
Zhou
F M
FM
Department of Neurobiology, University of Alabama, Birmingham, Alabama 35294, USA.
Hablitz
J J
JJ
D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D044406:Receptors, Serotonin, 5-HT3; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects*
D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D017366:Serotonin Receptor Agonists; D012701:Serotonin