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bioRxiv · 10.1101/595504

Chemogenetic activation of excitatory neurons alters hippocampal neurotransmission in a dose-dependent manner

Pati, S.·Salvi, S. S.·Kallianpur, M. V.·Banerjee, A.·Maiti, S.·Clement, J. P.·Vaidya, V. A.
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Abstract

Designer Receptors Exclusively Activated by Designer Drugs (DREADD)-based chemogenetic tools are extensively used to manipulate neuronal activity in a cell-type specific manner. Whole-cell patch-clamp recordings indicate membrane depolarization, coupled with increased neuronal firing rate, following administration of the DREADD ligand, Clozapine-N-Oxide (CNO) to activate the Gq-coupled DREADD, hM3Dq. Although hM3Dq has been used to enhance neuronal firing in order to manipulate diverse behaviors, often within thirty minutes to an hour post-CNO administration, the physiological effects on excitatory neurotransmission remain poorly understood. We investigated the influence of CNO-mediated hM3Dq DREADD activation on distinct aspects of hippocampal excitatory neurotransmission at the Schaffer collateral-CA1 synapse in hippocampal slices derived from mice expressing hM3Dq in Ca2+/calmodulin dependent protein kinase (CamKII)-positive excitatory neurons. Our results indicate a clear dose-dependent effect on fEPSP slope, with no change noted at the lower dose of CNO (1 {micro}M) and a significant, long-term decline in fEPSP slope observed at higher doses (5-20 {micro}M). Further, we noted a robust theta burst stimulus (TBS) induced long-term potentiation (LTP) in the presence of the lower CNO (1 {micro}M) dose, which was significantly attenuated at the higher CNO (20 {micro}M) dose. Whole-cell patch clamp recording revealed both complex dose-dependent regulation of excitability, and spontaneous and evoked activity of CA1 pyramidal neurons in response to hM3Dq activation across CNO concentrations. Our data indicate that CNO-mediated activation of the hM3Dq DREADD results in dose-dependent regulation of excitatory hippocampal neurotransmission, and highlight the importance of careful interpretation of behavioral experiments involving chemogenetic manipulation.

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Pati, S., Salvi, S. S., Kallianpur, M. V., Banerjee, A., Maiti, S., Clement, J. P., Vaidya, V. A.. 2019-04-01. Chemogenetic activation of excitatory neurons alters hippocampal neurotransmission in a dose-dependent manner. https://doi.org/10.1101/595504

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