Serotonergic modulation of supragranular neurons in rat sensorimotor cortex.
Numerous observations suggest diverse and modulatory roles for serotonin (5-HT) in cortex. Because of the diversity of cell types and multiple receptor subtypes and actions of 5-HT, it has proven difficult to determine the overall role of 5-HT in cortical function. To provide a broader perspective of cellular actions, we studied the effects of 5-HT on morphologically and physiologically identified pyramidal and nonpyramidal neurons from layers I-III of primary somatosensory and motor cortex. We found cell type-specific differences in response to 5-HT. Four cell types were observed in layer I: Cajal Retzius, pia surface, vertical axon, and horizontal axon cells. The physiology of these cells ranged from fast spiking (FS) to regular spiking (RS). In layers II-III, we observed interneurons with FS, RS, and late spiking physiology. Morphologically, these cells varied from bipolar to multipolar and included basket-like and chandelier cells. 5-HT depolarized or hyperpolarized pyramidal neurons and reduced the slow afterhyperpolarization and spike frequency. Consistent with a role in facilitating tonic inhibition, 5-HT2 receptor activation increased the frequency of spontaneous IPSCs in pyramidal neurons. In layers II-III, 70% of interneurons were depolarized by 5-HT. In layer I, 57% of cells with axonal projections to layers II-III (vertical axon) were depolarized by 5-HT, whereas 63% of cells whose axons remain in layer I (horizontal axon) were hyperpolarized by 5-HT. We propose a functional segregation of 5-HT effects on cortical information processing, based on the pattern of axonal arborization.
Foehring
R C
RC
Department of Neurology, University of Washington, Seattle, Washington 98195, USA. foehring@nb.utmem.edu
van Brederode
J F M
JF
Kinney
G A
GA
Spain
W J
WJ
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000378:metabolism; D008239:Lysine / Q000031:analogs & derivatives*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects; D044406:Receptors, Serotonin, 5-HT3; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013003:Somatosensory Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C013411:biocytin; D008239:Lysine; D011188:Potassium