Brain temperature and ethanol sensitivity in C57 mice: a radiotelemetric study

Dose-dependent alcohol effects on electroencephalogram: Sedation/anesthesia is qualitatively distinct from sleep

Alcohol is commonly used as a sleep inducer/aid by humans. However, individuals diagnosed with alcohol use disorders have sleep problems. Few studies have examined the effect of ethanol on physiological features of sedation and anesthesia, particularly at high doses. This study used polysomnography and a rapid, unbiased scoring of vigilance states with an automated algorithm to provide a thorough characterization of dose-dependent acute ethanol effects on sleep and electroencephalogram (EEG) power spectra in C57BL/6J male mice. Ethanol had a narrow dose-response effect on sleep. Only a high dose (4.0 g/kg) produced a unique, transient state that could not be characterized in terms of canonical sleep-wake states, so we dubbed this novel state Drug-Induced State with a Characteristic Oscillation in the Theta Band (DISCO-T). After this anesthetic effect, the high dose of alcohol promoted NREM sleep by increasing the duration of NREM bouts while reducing wake. REM sleep was differentially responsive to the circadian timing of ethanol administration. EEG power spectra proved more sensitive to ethanol than sleep measures as there were clear effects of ethanol at 2.0 and 4.0 g/kg doses. Ethanol promoted delta oscillations and suppressed faster frequencies, but there were clear, differential effects on wake and REM EEG power based on the timing of the ethanol injection. Understanding the neural basis of the extreme soporific effects of high dose ethanol may aid in treating acute toxicity brought about by patterns of excessive binge consumption commonly observed in young people.

Perspectives for Ag2S NIR-II nanoparticles in biomedicine: from imaging to multifunctionality

Research on near-infrared (NIR) bioimaging has progressed very quickly in the past few years, as fluorescence imaging is reaching a credible implementation as a preclinical technique. The applications of NIR bioimaging in theranostics have contributed to its increasing impact. This has brought about the development of novel technologies and, simultaneously, of new contrast agents capable of acting as efficient NIR optical probes. Among these probes, Ag₂S nanoparticles (NPs) have attracted increasing attention due to their temperature-sensitive NIR-II emission, which can be exploited for deep-tissue imaging and thermometry, and their heat delivery capabilities. This multifunctionality makes Ag₂S NPs ideal candidates for theranostics. This review presents a critical analysis of the synthesis routes, properties and optical features of Ag₂S NPs. We also discuss the latest and most remarkable achievements enabled by these NPs in preclinical imaging and theranostics, together with a critical assessment of their potential to face forthcoming challenges in biomedicine.

Effects of Ketamine Compared with Urethane Anesthesia on Vestibular Sensory Evoked Potentials and Systemic Physiology in Mice

The injectable anesthetic mixture ketamine-xylazine is commonly used for electrophysiologic experiments in laboratory animals, especially rodents. General anesthesia can induce significant changes in systemic physiology, including those that compromise neural function, thus introducing research confounds. The extent of such concerns varies by agent. Here in mice, we compared the effects of ketamine-xylazine and urethane-xylazine anesthesia on systemic physiologic parameters and the vestibular sensory evoked potential (VsEP), a tool used commonly to assess peripheral vestibular function. Urethane-xylazine anesthesia provided longer anesthesia, prolonged survival times, and less compromised respiratory and cardiovascular function, compared with ketamine-xylazine. In the absence of countermeasures, mice anesthetized with either ketamine-xylazine or urethane-xylazine showed evidence of hypoxemia and fluctuations in brain temperature, heart rate, respiration rate, and VsEP response latency. The levels of hypoxemia had no effect on VsEP response parameters over the period of study (2 to 5 h). Hypoxemia was effectively countered with O2 supplementation, which stabilized respiratory rates and improved mean survival times by 160% in mice anesthetized with ketamine-xylazine. Monitoring and controlling brain temperature reduced variation in VsEP latency. VsEP thresholds, latencies, and amplitudes did not differ between mice under ketamine-xylazine compared with urethane-xylazine when the brain temperature was held at the same set point. These findings demonstrate that urethane-xylazine provides improved systemic physiologic conditions during anesthesia in mice and may be substituted for ketamine-xylazine in studies using the VsEP to evaluate peripheral vestibular function. Such advantages may prove useful to research in other neuroscience areas and might reduce the number of animals used to achieve adequate sample sizes.

A method for hypothermia-induction and maintenance allows precise body and brain temperature control in mice

The benefits as well as mechanisms of hypothermia in brain injuries are actively studied at the bench and in the clinic. However, methods used in controlling hypothermia vary among laboratories, and usually brain temperatures are not monitored directly in animals due to the need for an invasive procedure. Here we show a method, water immersion technique, which we developed recently to regulate body temperature in mice during hypothermia process. This method significantly reduced the temperature variation around target temperature. Importantly, this method demonstrated a parallel and consistent relationship between rectal temperature and brain temperature (the brain temperature was consistently 0.5C higher than rectal temperature) throughout hypothermia maintenance. This technique may be well adapted to hypothermia studies in mice and other rodents, especially to the assessment and regulation of brain temperature during studies.

Temperature dependence of ethanol depression in mice: dose response

Manipulation of body temperature during intoxication significantly alters brain sensitivity to ethanol. The current study tested the generality of this effect within the hypnotic dose range. Drug naive, male C57BL/6J mice were injected with 3.2, 3.6, or 4.0 g/kg ethanol (20% w/v) and were exposed to 1 of 7 designated temperatures from 13 degrees to 34 degrees C to manipulate body temperature during intoxication. Rectal temperature at return of righting reflex (RORR) was significantly, positively correlated with loss of righting reflex (LORR) duration and significantly, negatively correlated with blood ethanol concentration (BEC) at RORR at all three doses. These results indicate that increasing body temperature during intoxication increased ethanol sensitivity in C57 mice at all three doses tested and demonstrate the generality of temperature dependence across hypnotic doses in these animals. Interestingly, the LORR duration was dose-dependent at each ambient temperature, but the degree of body temperature change and the BEC at RORR were not dose-dependent. Overall, these results emphasize the importance of body temperature as a variable in ethanol research.

Use of telemetry to record electrocardiogram and heart rate in freely moving mice

This paper describes for the first time the possibility to record the electrocardiogram (ECG) and heart rate (HR) with a commercially available telemetry and data acquisition system in freely moving mice. The system comprises a telemetry transmitter implanted in the peritoneal cavity and a receiver, placed underneath the home cage, an A/D converter (MacLab) and a Macintosh LC II 4/80 computer with software (MacLab, Chart/Scope). The raw analog ECG data are digitized within the MacLab and can be converted to HR data additionally. The effects of surgery for implanting the transmitter, handling and anesthesia by either Nembutal or a mixture of Hypnorm, Dormicum, and water, on the changes in ECG and HR were examined. The telemetry system for recording the ECG and HR provides an accurate and reliable method for monitoring the direct effects of handling on HR. By using this telemetry system, we maintain that measurements in freely moving animals are more efficient, reliable, and less labor-intensive than the measurement techniques described in the literature thus far.