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Histamine facilitates GABAergic transmission in the rat entorhinal cortex: Roles of H 1 and H 2 receptors, Na + ‐permeable cation channels, and inward rectifier K + channels
Author(s) -
Cilz Nicholas I.,
Lei Saobo
Publication year - 2017
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.22718
Subject(s) - chemistry , depolarization , neuroscience , gabaergic , neurotransmission , biophysics , inhibitory postsynaptic potential , entorhinal cortex , membrane potential , receptor , biology , hippocampal formation , biochemistry
In the brain, histamine (HA) serves as a neuromodulator and a neurotransmitter released from the tuberomammillary nucleus (TMN). HA is involved in wakefulness, thermoregulation, energy homeostasis, nociception, and learning and memory. The medial entorhinal cortex (MEC) receives inputs from the TMN and expresses HA receptors (H 1 , H 2 , and H 3 ). We investigated the effects of HA on GABAergic transmission in the MEC and found that HA significantly increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) with an EC 50 of 1.3 µM, but failed to significantly alter sIPSC amplitude. HA‐induced increases in sIPSC frequency were sensitive to tetrodotoxin (TTX), required extracellular Ca 2+ , and persisted when GDP‐β‐S, a G‐protein inactivator, was applied postsynaptically via the recording pipettes, indicating that HA increased GABA release by facilitating the excitability of GABAergic interneurons in the MEC. Recordings from local MEC interneurons revealed that HA significantly increased their excitability as determined by membrane depolarization, generation of an inward current at −65 mV, and augmentation of action potential firing frequency. Both H 1 and H 2 receptors were involved in HA‐induced increases in sIPSCs and interneuron excitability. Immunohistochemical staining showed that both H 1 and H 2 receptors are expressed on GABAergic interneurons in the MEC. HA‐induced depolarization of interneurons involved a mixed ionic mechanism including activation of a Na + ‐permeable cation channel and inhibition of a cesium‐sensitive inward rectifier K + channel, although HA also inhibited the delayed rectifier K + channels. Our results may provide a cellular mechanism, at least partially, to explain the roles of HA in the brain. © 2017 Wiley Periodicals, Inc.