Noninvasive, High-throughput Determination of Sleep Duration in Rodents

Summary

We describe a high-throughput method of measuring sleep by means of activity-based home-cage monitoring. This method offers advantages over traditional EEG-based methods. It is well validated for the determination of total sleep duration and can be a powerful tool to monitor sleep in rodent models of human disease.

Abstract

Traditionally, sleep is monitored by an electroencephalogram (EEG). EEG studies in rodents require surgical implantation of the electrodes followed by a long recovery period. To perform an EEG recording, the animal is connected to a receiver, creating an unnatural tether to the head-mount. EEG monitoring is time consuming, carries risk to the animal, and is not a completely natural setting for the measurement of sleep. Alternative methods to detect sleep, particularly in a high-throughput fashion, would greatly advance the field of sleep research. Here, we describe a validated method for detecting sleep via activity-based home-cage monitoring. Previous studies have shown that sleep assessed via this method has a high degree of agreement with sleep defined by traditional EEG-based measures. Whereas this method is validated for total sleep time, it is important to note that sleep bout duration should be assessed by an EEG which has better temporal resolution. The EEG can also differentiate rapid eye movement (REM) and non-REM sleep, giving more detail about the exact nature of sleep. Nevertheless, activity-based sleep determination can be used to analyze multiple days of undisturbed sleep and to assess sleep as a response to an acute event (like stress). Here, we show the power of this system to detect the response of mice to daily intraperitoneal injections.

Introduction

Sleep has important functions for the restoration of the body and brain following the daily burden of wakefulness¹. It has been shown that sleep plays a role in memory retention and general brain plasticity¹. The EEG is the gold standard to detect sleep². In rodents, EEG monitoring requires surgical implantation of electrodes affixed to a head-mount, after which the animal needs a period of time to recover². After the recovery, the animal is attached to the recording device and is given another period of habituation². Because of these necessary perio....

Protocol

All the procedures were approved by the National Institute of Mental Health Animal Care and Use Committee and performed in accordance with the National Institutes of Health Guidelines on the Care and Use of Animals.

1. Setting up the Sleep Detection Units

1. Purchase the desired number of units and software.
2. Follow the instructions to set up the monitoring systems.
   1. Align a detector opposite to an emitter. Make sure the infrared beams are facing inwards and are aligned at the same height.
   2. Use the provided screws to position the detectors and emitters at the desired height on the metal stand. This hei....

Results

To determine the effect of daily injections on sleep and whether animals habituate to the injections, we performed daily IP injections for 14 consecutive days at 9:00 AM (light cycle began at 6:00 AM) and recorded sleep duration in 12 Fmr1 KO C57Bl/6J mice. We used a within subjects' design, injecting each animal with normal saline for 4 consecutive days (Days 1-4) and then 30% cyclodextrin for the following ten consecutive days (Days 5-14). Cyclodextrin was selected because it c.......

Discussion

Here, we present a noninvasive, high-throughput method for determination of sleep duration based on activity monitoring in the home-cage. This method of assessment of total sleep time has been validated against EEG studies³. Activity-based home-cage monitoring is simple, noninvasive, and applicable to population studies in large numbers of animals. It is limited in that it cannot give detailed information about sleep (such as sleep bout duration and sleep stages).

Pitfa.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Comprehensive Lab Animal Monitoring System (CLAMS)	Columbus Instruments		Equipment and software to analyze sleep duration
Captisol Research Grade	Captisol	RC-0C7-100	Captisol for dissolving hydrophobic compounds
30 G BD Needle 1/2 inch	BD	305106	Needle for injections
BD Disposable Syringes	Fisher	14-823-30	Syringes for injections
B6.129P2-Fmr1tm1Cgr/J	Jackson Labs	3025	Fmr1 KO mice
Super Mouse 750 Mouse Cage	Lab Products, Inc.		Homecages for the mice
SANI-Chips Bedding	PJ Murphys		Bedding for the mice