Song, S. M. | bioRxiv Science

bioRxiv2022

Effects of clozapine-N-oxide and compound 21 on sleep in laboratory mice

Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) are chemogenetic tools for remote control of targeted cell populations using chemical actuators that bind to modified receptors. Despite the popularity of DREADDs in neuroscience and sleep research, potential effects of the DREADD actuator clozapine-N-oxide (CNO) on sleep have never been systematically tested. Here we show that intraperitoneal injections of commonly used CNO doses (1, 5, and 10 mg/kg) alter sleep in wild-type male laboratory mice. Using electroencephalography (EEG) and electromyography (EMG) to analyse sleep, we found a dose-dependent suppression of rapid eye-movement (REM) sleep, changes in EEG spectral power during non-REM (NREM) sleep, and altered sleep architecture in a pattern previously reported for clozapine. Effects of CNO on sleep could arise from back-metabolism to clozapine or binding to endogenous neurotransmitter receptors. Interestingly, we found that the novel DREADD actuator, compound 21 (C21, 3 mg/kg), similarly modulates sleep despite a lack of back-metabolism to clozapine. Our results demonstrate that both CNO and C21 can modulate sleep of mice not expressing DREADD receptors. This implies that back-metabolism to clozapine is not the sole mechanism underlying side effects of chemogenetic actuators. Therefore, any chemogenetic experiment should include a DREADD-free control group injected with the same CNO, C21 or newly developed actuator. We suggest that electrophysiological sleep assessment could serve as a sensitive tool to test the biological inertness of novel chemogenetic actuators.

neuroscience↗

bioRxiv2020

Identification of a novel breathing circuit that controls pain and anxiety

Alleviating pain with controlled breathing has been practiced throughout human history. Despite its wide use and long history, a neural circuit-based understanding of the pain-breathing interaction is largely lacking. Here we report a novel breathing circuit that regulates non-homeostatic breathing rhythm, as well as pain and anxiety. We identify that a cluster of neurons expressing the Oprm1 gene, which encodes the -opioid receptor (MOR) in the lateral subdivision of parabrachial nucleus (PBLOprm1), directly regulates breathing rate in mice by conveying signals from the limbic areas to respiratory rhythm generating neurons in the medullary preBotzinger Complex (preBotC). In addition, we found that pain signals rapidly increase breathing rate by activating these neurons in both awake and anesthetized mice. Inactivating these neurons not only decreases the breathing rate, but it also substantially decreases anxiety-like behaviors and induces strong appetitive behaviors. Furthermore, PBLOprm1 inactivation alleviates pain by attenuating the perception of the affective-motivational aspect of pain. These results suggest that PBLOprm1 neurons play a critical role in the non-homeostatic regulation of breathing and in the regulation of pain and anxiety through breathing.

neuroscience↗