Effects of temperature on sleep in the developing rat

A Novel Continuously Recording Approach for Unraveling Ontogenetic Development of Sleep-Wake Cycle in Rats

Sleep-wake development in postnatal rodent life could reflect the brain maturational stages. As the altricial rodents, rats are born in a very undeveloped state. Continuous sleep recording is necessary to study the sleep-wake cycle profiles. However, it is difficult to realize in infant rats since they rely on periodic feeding before weaning and constant warming and appropriate EEG electrodes. We developed a new approach including two types of EEG electrodes and milk-feeding system and temperature-controlled incubator to make continuously polysomnographic (PSG) recording possible. The results showed that there was no evident difference in weight gaining and behaviors between pups fed through the milk-feeding system and warmed with temperature-controlled incubator and those kept with their dam. Evolutional profiles of EEG and electromyogram (EMG) activities across sleep-wake states were achieved perfectly during dark and light period from postnatal day (P) 11 to P75 rats. The ontogenetic features of sleep-wake states displayed that the proportion of rapid eye movement (REM) was 57.0 ± 2.4% and 59.7 ± 1.7% and non-REM (NREM) sleep was 5.2 ± 0.8% and 4.9 ± 0.5% respectively, in dark and light phase at P11, and then REM sleep progressively decreased and NREM sleep increased with age. At P75, REM sleep in dark and light phase respectively, reduced to 6.3 ± 0.6% and 6.9 ± 0.5%, while NREM correspondingly increased to 37.5 ± 2.1% and 58.4 ± 1.7%. Wakefulness from P11 to P75 in dark phase increased from 37.8 ± 2.2% to 56.2 ± 2.6%, but the change in light phase was not obvious. P20 pups began to sleep more in light phase than in dark phase. The episode number of vigilance states progressively decreased with age, while the mean duration of that significantly increased. EEG power spectra in 0.5–4 Hz increased with age accompanied with prolonged duration of cortical slow wave activity. Results also indicated that the dramatic changes of sleep-wake cycle mainly occurred in the first month after birth. The novel approaches used in our study are reliable and valid for continuous PSG recording for infant rats and unravel the ontogenetic features of sleep-wake cycle.

Methodologic recommendations and possible interpretations of video-EEG recordings in immature rodents used as experimental controls: A TASK1-WG2 report of the ILAE/AES Joint Translational Task Force

The use of immature rodents to study physiologic aspects of cortical development requires high‐quality recordings electroencephalography (EEG) with simultaneous video recording (vEEG) of behavior. Normative developmental vEEG data in control animals are fundamental for the study of abnormal background activity in animal models of seizures or other neurologic disorders. Electrical recordings from immature, freely behaving rodents can be particularly difficult because of the small size of immature rodents, their thin and soft skull, interference with the recording apparatus by the dam, and other technical challenges. In this report of the TASK1 Working Group 2 (WG2) of the International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force, we provide suggestions that aim to optimize future vEEG recordings from immature rodents, as well as their interpretation. We focus on recordings from immature rodents younger than 30 days old used as experimental controls, because the quality and correct interpretation of such recordings is important when interpreting the vEEG results of animals serving as models of neurologic disorders. We discuss the technical aspects of such recordings and compare tethered versus wireless approaches. We also summarize the appearance of common artifacts and various patterns of electrical activity seen in young rodents used as controls as a function of behavioral state, age, and (where known) sex and strain. The information herein will hopefully help improve the methodology of vEEG recordings from immature rodents and may lead to results and interpretations that are more consistent across studies from different laboratories.

Sedative and anxiolytic effects of the extracts of the leaves of Stachytarpheta cayennensis in mice

The leaves are used ethnomedicinally in Nigeria and other parts of the world for insomnia and anxiety among other uses. The investigations sought scientific evidence for the ethnomedicinal use of the leaves for the management of insomnia and anxiety as well as the neural mechanisms for the activities. The sedative and anxiolytic effects of the extracts of the leaves of Stachytarpheta cayennensis were examined in this study. The methanolic extract (5-50 mg/kg, i.p.) as well as the ethylacetate (10-50 mg/kg, i.p.), butanol and aqueous fractions (5-50 mg/kg, i.p.) of the extract were examined. Sedation was assessed as reduced novelty-induced rearing (NIR), reduced spontaneous locomotor activity (SLA) and increased pentobarbitone-induced sleeping time (PIST) in mice. The anti-anxiety effect (methanol 2.5-5.0; butanol 5.0; aqueous 20.0; ethylacetate 25.0 mg/kg, i.p.) was assessed using an elevated plus maze. LD50 was calculated for the extract and the fractions after the intraperitoneal route of administration using the Locke method. The methanolic extract, the butanol and the aqueous fractions inhibited rearing and spontaneous locomotion but prolonged pentobarbitone induced sleep. The ethylacetate fraction however increased both rearing and locomotion and decreased pentobarbitone sleeping time. The butanol and aqueous fractions, but not the methanol extract showed indices of open arm avoidance consistent with anti-anxiety effect. Naltrexone (2.5 mg/kg, i.p.) reversed the inhibition of rearing, locomotion and prolongation of pentobarbitone sleep due to the aqueous fraction of the extract. Flumazenil (2mg/kg, i.p.) abolished the effects of both methanolic extract and the butanol fraction on rearing, locomotion, pentobarbitone sleep and anxiety model. The methanolic extract, the butanol and aqueous fractions possess sedative activity while the ethylacetate fraction possesses stimulant property. The anxiolytic effect was found in both the aqueous fraction and the butanol fraction but not in the main methanol extract and also not in the ethylacetate fraction. Flumazenil, blocked the effect of the leaves of Stachytarpheta cayennensis on rearing, locomotion and elevated plus maze suggesting that GABA receptors are involved in the observed sedative and anxiolytic activities. This study also found opioid receptors involved in the sedative activity of the leaves of Stachytarpheta cayennensis. The rationale for the ethnomedicinal use of the leaves for the management of insomnia and anxiety were confirmed scientifically in this study.