Two distinct effects of 5-hydroxytryptamine on single cortical neurons.
The ability of the indoleamine serotonin (5-hydroxytryptamine; 5-HT) to alter membrane characteristics of neocortical neurons was analyzed using intracellular recording techniques. The present study demonstrates that 5-HT primarily depolarized 68% of cortical neurons probably by decreasing a resting K+ conductance, an effect blocked by the antagonists ritanserin and cinanserin and apparently mediated by 5-HT2 receptors. A hyperpolarization associated with an increased conductance state and insensitive to 5-HT2 antagonists was observed in 26% of the neurons and could be mimicked by the selective 5-HT1A agonist (+/-)-8-hydroxy-2-(di-N-propyl-amino)tetralin (8-OH-DPAT). Therefore cortical pyramidal neurons contain at least two distinct functional 5-HT receptors whose activation produces opposing effects on membrane potential and conductance.
D000818:Animals; D002928:Cinanserin / Q000494:pharmacology; D004553:Electric Conductivity; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010880:Piperidines / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011712:Pyramidal Tracts / Q000187:drug effects / Q000502:physiology; D016713:Ritanserin; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013003:Somatosensory Cortex / Q000187:drug effects / Q000502:physiology*
D010880:Piperidines; D012702:Serotonin Antagonists; D016713:Ritanserin; D012701:Serotonin; D002928:Cinanserin; D011188:Potassium