1. Serotonergic modulation of supragranular neurons in rat sensorimotor cortex.
- Author
-
Foehring RC, van Brederode JF, Kinney GA, and Spain WJ
- Subjects
- Action Potentials drug effects, Action Potentials physiology, Animals, Excitatory Amino Acid Antagonists pharmacology, GABA Antagonists pharmacology, In Vitro Techniques, Interneurons drug effects, Interneurons metabolism, Membrane Potentials drug effects, Membrane Potentials physiology, Neural Inhibition drug effects, Neural Inhibition physiology, Neurons drug effects, Patch-Clamp Techniques, Potassium metabolism, Pyramidal Cells drug effects, Pyramidal Cells metabolism, Rats, Receptors, Serotonin drug effects, Receptors, Serotonin, 5-HT3, Serotonin pharmacology, Serotonin Receptor Agonists pharmacology, Somatosensory Cortex cytology, Somatosensory Cortex drug effects, Lysine analogs & derivatives, Neurons metabolism, Serotonin metabolism, Somatosensory Cortex metabolism
- Abstract
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.
- Published
- 2002