Effect of Inactivation of Prefrontal Cortex on Sleep-Wake States in Rat

Abstract

There is a large body of literature to support subcortical regulation of sleep-wake states, but there have been limited studies to investigate the role of cortex in sleep-wake regulation. Previously, we have demonstrated that cholinergic stimulation of prefrontal cortex can reverse general anesthesia and promote wakefulness in unanesthetized rats, and there is emerging evidence to suggest that the prefrontal cortex might be a critical node in arousal state control. To better understand the direct role of prefrontal cortex in the regulation of sleep-wake states, we quantified the effect of prefrontal cortex inactivation, via local tetrodotoxin (156 μM) infusion, on sleep architecture. Under surgical isoflurane anesthesia, adult Sprague Dawley rats (n=7 male) were instrumented with electrodes to record electroencephalogram (EEG) from frontal and parietal cortices, and electromyogram (EMG) from dorsal nuchal muscles. In addition, a bilateral guide cannula was implanted aimed at the medial prefrontal cortex for tetrodotoxin infusion. After at least a week of post-surgical recovery and conditioning to the recording chambers, rats received bilateral microinjection (500 nL) of either 156 μM tetrodotoxin or 0.9% saline (vehicle control). The tetrodotoxin and 0.9% saline infusions were performed 30-minutes before the start of lights-OFF period (8:00 pm) after which EEG and EMG data were recorded for 24h across dark and light cycles. The EEG and EMG data were manually scored (SleepSign, Kissei Comtec Inc.) in 4-second intervals into wakefulness, slow-wave sleep, and rapid eye movement sleep, and then averaged in 3h bins across 24h recording period. A linear mixed model was used to compare the changes in percent time spent in each state, mean duration per episode for each state, and mean number of episodes for each state, between the vehicle control and tetrodotoxin-infusion sessions. Inactivation of prefrontal cortex via tetrodotoxin infusion produced long-lasting statistically significant increase in slow-wave sleep (p<0.05 for 0-3h, 4-6h, 7-9h, 10-12h, 13-15, 16-18, 22-24) and decrease in wakefulness (p<0.05 for 0-3h, 4-6h, 10-12h) and rapid eye movement sleep (p<0.05 for 7-9h, 10-12h, 13-15h). These data further support a causal contribution of prefrontal cortex in regulating arousal states. This work was supported by the National Institutes of Health (Bethesda, MD, USA) grant (R01 GM111293) to GAM and DP, and funding from the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.