Serotonin modulates the excitatory synaptic transmission in the dentate granule cells

Serotonergic fibers from the raphe nuclei project to the hippocampal formation, the activity of which is known to modulate the inhibitory interneurons in the dentate gyrus. On the other hand, serotonergic modulation of the excitatory synapses in the dentate gyrus is not well examined. In the present...

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Bibliographic Details
Published in:Journal of neurophysiology 2016-06, Vol.115 (6), p.2997-3007
Main Authors: Nozaki, Kanako, Kubo, Reika, Furukawa, Yasuo
Format: Article
Language:English
Subjects:
Animals
Animals, Newborn
Cellular and Molecular Properties of Neurons
Computer Simulation
Dentate Gyrus - cytology
Electric Stimulation
Excitatory Postsynaptic Potentials - drug effects
Female
GABA Antagonists - pharmacology
In Vitro Techniques
Male
Models, Neurological
Mossy Fibers, Hippocampal - physiology
Neurons - drug effects
Neurons - physiology
Perforant Pathway - physiology
Picrotoxin
Piperazines - pharmacology
Pyridines - pharmacology
Rats
Rats, Wistar
Serotonin - pharmacology
Serotonin Antagonists - pharmacology
Statistics, Nonparametric
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Summary:Serotonergic fibers from the raphe nuclei project to the hippocampal formation, the activity of which is known to modulate the inhibitory interneurons in the dentate gyrus. On the other hand, serotonergic modulation of the excitatory synapses in the dentate gyrus is not well examined. In the present study, we examined the effects of 5-HT on the excitatory postsynaptic potentials (EPSPs) in the dentate granule cells evoked by the selective stimulation of the lateral perforant path (LPP), the medial perforant path (MPP), or the mossy cell fibers (MCF). 5-HT depressed the amplitude of unitary EPSPs (uEPSPs) evoked by the stimulation of LPP or MPP, whereas uEPSPs evoked by MCF stimulation were little affected. The effect was partly explained by the decrease of the resting membrane resistance following the activation of 5-HT1A receptors, which was confirmed by computer simulations. We also found that the probability of evoking uEPSP by LPP stimulation but not MPP or MCF stimulation was reduced by 5-HT and that the paired-pulse ratio of LPP-evoked EPSP but not that of MPP- or MCF-evoked ones was increased by 5-HT. These effects were blocked by 5-HT2 antagonist, suggesting that the transmitter release in the LPP-granule cell synapse is inhibited by the activation of 5-HT2 receptors. The present results suggest that 5-HT can modulate the EPSPs in the dentate granule cells by at least two distinct mechanisms.
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.00064.2016