Chemogenetic Activation of Excitatory Neurons Alters Hippocampal Neurotransmission in a Dose-Dependent Manner

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 30 min to 1 h after 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 α (CamKIIα)-positive excitatory neurons. Our results indicate a clear dose-dependent effect on field EPSP (fEPSP) slope, with no change noted at the lower dose of CNO (1 μM) and a significant, long-term decline in fEPSP slope observed at higher doses (5–20 μM). Further, we noted a robust θ burst stimulus (TBS) induced long-term potentiation (LTP) in the presence of the lower CNO (1 μM) dose, which was significantly attenuated at the higher CNO (20 μM) 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.

Chronic postnatal chemogenetic activation of forebrain excitatory neurons evokes persistent changes in mood behavior

“…Given that thus far very few studies have used chemogenetic strategies during developmental time windows ( Teissier et al, 2020 ; Wong et al, 2018 ), we characterized the consequences of hM3Dq DREADD activation of forebrain excitatory neurons in the postnatal window using both electrophysiological and biochemical approaches. Our observation of hM3Dq DREADD-mediated induction of robust spiking activity in postnatal slices parallels observations made in adulthood ( Alexander et al, 2009 ; Pati et al, 2019 ). Chronic chemogenetic hM3Dq DREADD activation during postnatal life enhanced neuronal activity marker expression in the hippocampus and cortex, as well as increased network activity, enhanced spontaneous excitatory events, and reduced spontaneous inhibitory events in CA1 pyramidal neurons in PNCNO-treated mouse pups.…”

nNOS-expressing interneurons control basal and behaviorally evoked arterial dilation in somatosensory cortex of mice

“…When we pan-neuronally expressed hM3D-G(q) DREADDs, which will increase excitability and intracellular calcium levels (Alexander et al, 2009;Pati et al, 2019), activation of the DREADDs with CNO injections caused increases in gamma-band power relative to vehicle (Fig. 2F,basal 18.6±11.2%,p<0.02;locomotion,43.6±15.0%, ).…”

Induced neuronal activity does not attenuate amyloid beta‐induced synaptic loss in vitro

“…In addition, it has been reported that 20 μmol/L CNO results in faster increase in intracellular calcium levels compared to 1 μmol/L CNO in primary hippocampal neurons and that CNO at more than 20 μmol/L would not result in more enhanced neuronal activity …”