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Serotonin reduces inhibition via 5-HT1A receptors in area CA1 of rat hippocampal slices in vitro

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Item Type:Article
Title:Serotonin reduces inhibition via 5-HT1A receptors in area CA1 of rat hippocampal slices in vitro
Creators Name:Schmitz, D., Empson, R.M. and Heinemann, U.
Abstract:We studied the effects of serotonin (5-HT) on intrinsic and synaptic responses of hippocampal CA1 cells. The effects were partially mimicked by the 5-HT1A receptor agonist, 8-OH-DPAT, and prevented by the 5-HT1A receptor antagonist, NAN-190. Polysynaptic fast and slow inhibitory postsynaptic potentials (IPSPs) were reduced in amplitude by 60-70% following application of both 5-HT and 8-OH-DPAT. Monosynaptic fast IPSPs were reduced by 60% and slow IPSPs by 90% following application of both drugs. Since there is a temporal overlap of fast and slow IPSPs, the reduction in fast IPSPs could have arisen indirectly from the larger effect of 5-HT on slow IPSPs. To overcome this problem we blocked the slow IPSPs with new, potent GABA-B antagonists, but still observed a similar reduction in the fast IPSP with 5-HT and 8-OH-DPAT. However, the reductions in the fast IPSPs could also have arisen from the 5-HT-induced total conductance increases. Using single-electrode voltage clamp and intracellular K+ channel blockers we still observed similar changes. 5-HT and 8-OH-DPAT had no effect upon GABA-A-mediated currents evoked by iontophoretic GABA application to the dendrites or the soma of CA1 pyramidal cells, Putative inhibitory internuerons were hyperpolarized by 5-HT and their evoked EPSPs strongly reduced by 5-HT and 8-OH-DPAT. Our data indicate that 5-HT modulates fast and slow synaptic inhibition of principal cells using presynaptic mechanisms involving the inhibition of inhibitory interneurons.
Keywords:Hippocampus, CA1 Pyramidal Cells, Serotonin, 8-OH-DPAT, Inhibition, Interneurons, Animals, Rats
Source:Journal of Neuroscience
Publisher:Society for Neuroscience
Page Range:7217-7225
Date:November 1995
Official Publication:http://www.jneurosci.org/content/15/11/7217.abstract
PubMed:View item in PubMed

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