Despite evidence linking the serotoninergic (5-HT) dorsal raphe nucleus (DRN) with the regulation of sleep-wake states, lesions of serotoninergic DRN neurons in rats minimally alter sleep-wake cycle. The lesion studies are however difficult to interpret given possible compensation mechanisms, lack of specificity of the toxins to induce the lesion, and incomplete cell loss. The DRN is heterogeneous and contains 5-HT, dopaminergic, GABAergic, and glutamatergic neurons. Thus, cell-type specific approaches are needed to define the individual contribution of DRN cell populations, including serotoninergic DRN neurons, to sleep-wake cycle control. Here we employed a conditional chemogenetic approach to selectively and acutely activate serotoninergic DRN neurons and analyzed behavioral and electrographic outcomes. Male serotonin reuptake transporter (SERT)-Cre driver mice were stereotaxically injected with a Cre-dependent adeno-associated viral (AAV) vector expressing an excitatory chemogenetic system (AAV-FLEX-hM3Dq-mCherry) into the DRN. The mice were then surgically implanted with EEG/EMG recording electrodes to monitor sleep-wake cycle. Injections of the hM3Dq ligand, clozapine-N-oxide (CNO; 0.3mg/kg, i.p.) were given at 9:00am (a time of high sleep pressure in the nocturnal mouse) and 6:00pm (a time of low sleep pressure in the mouse). Changes in behavioral state were determined from EEG/EMG and behavioral analysis from video monitoring. Eutopic expression of Cre and hM3Dq in the SERT-Cre mouse was confirmed using standard histological techniques. Administration of CNO at 9:00am produced a significant increase in NREM sleep during the first post injection hour and a significant reduction in latency to sleep. In addition, we report no statistically significant reduction in anxiety following acute and selective activation of serotoninergic DRN neurons in two anxiety-related behavioral tests, the open field and the elevated plus maze. While these results suggest that activation of serotoninergic neurons in the DRN may not produce anxiolytic effects, further studies will be required to confirm this. / 2019-07-03T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/30772 |
| Date | 03 July 2018 |
| Creators | Broadhurst, Rebecca Yu |
| Contributors | Soghomonian, Jean-Jacques |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution-NonCommercial-NoDerivatives 4.0 International, http://creativecommons.org/licenses/by-nc-nd/4.0/ |
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