Gene expression analysis in the mouse brainstem identifies cart and nesfatin as neuropeptides coexpressed in the Calbindin-positive neurons of the Nucleus papilio

Abstract

Study Objectives: The brainstem contains several neuronal populations, heterogeneous in terms of neurotransmitter/neuropeptide content, which are important for controlling various aspects of the rapid eye movement (REM) phase of sleep. Among these populations are the Calbindin (Calb)-immunoreactive NPCalb neurons, located in the Nucleus papilio, within the dorsal paragigantocellular nucleus (DPGi), and recently shown to control eye movement during the REM phase of sleep. Methods: We performed in-depth data mining of the in situ hybridization data collected at the Allen Brain Atlas, in order to identify potentially interesting genes expressed in this brainstem nucleus. Our attention focused on genes encoding neuropeptides, including Cart (Cocaine and Amphetamine Regulated Transcripts) and Nesfatin 1. Results: While nesfatin 1 appeared ubiquitously expressed in this Calb-positive neuronal population, Cart was coexpressed in only a subset of these glutamatergic NPCalb neurons. Furthermore, an REM sleep deprivation and rebound assay performed with mice revealed that the Cart-positive neuronal population within the DPGi was activated during REM sleep (as measured by c-fos immunoreactivity), suggesting a role of this neuropeptide in regulating some aspects of REM sleep. Conclusions: The assembled information could afford functional clues to investigators, conducive to further experimental pursuits. Statement of Significance Several physiological and behavioral features are characteristics of the rapid eye movement (REM) phase of sleep, also called paradoxical sleep. These include muscle atonia, desynchronized EEG activity, vivid dreaming, and rapid eye movements. A small cluster of Calbindin-immunoreactive neurons (namely, the Nucleus papilio) has been recently identified in the brainstem and shown to be both necessary and sufficient for triggering eye movement during REM sleep. In the present study, we performed data mining of the in situ hybridization data collected at the Allen Brain Atlas, in order to identify genes expressed in these neurons. Our data show that the neuropeptide Cart (Cocaine and Amphetamine Regulated Transcript) is expressed in some of these Calbindin-immunoreactive neurons and that these Cart-neurons are activated during REM sleep.