# Synergistic effects of combined hypnotic drugs on sleep in mice

## TL;DR

This study shows that combining two sleep drugs in mice leads to better sleep effects than using either drug alone, possibly by changing brain activity and neurotransmitter levels.

## Contribution

The novel finding is the synergistic effect of combining dexmedetomidine and eszopiclone on sleep in mice, along with the underlying neural and neurotransmitter mechanisms.

## Key findings

- The combination of DMED and ESZ synergistically prolonged non-rapid eye movement (NREM) sleep in mice.
- The combination increased c-Fos positive neurons in the VLPO and decreased them in the TMN.
- The drug combination altered brain neurotransmitter levels, reducing excitatory and increasing inhibitory neurotransmitters.

## Abstract

To investigate the interaction and potential mechanisms of the combined administration of dexmedetomidine (DMED) and eszopiclone (ESZ) on sleep in mice.

The effects of DMED, ESZ and the combination of the two drugs on the sleep status of mice were investigated by using the loss of righting reflex (LORR) as an indicator, the sleep-related parameters were recorded, and the interactions of the combination of DMED and ESZ on sleep were determined by isobolographic analysis. The effects of DMED and ESZ on sleep structure, the regulation of c-Fos protein expression in the ventrolateral preoptic area (VLPO) and the tuberomammillary nucleus (TMN) and the regulation of neurotransmitter levels were further investigated by combining electroencephalogram/electromyogram (EEG/EMG) sleep phase analysis, c-Fos immunofluorescence, and neurotransmitter content measurements in the brain.

Isobolographic analysis demonstrated that the combination of DMED and ESZ had a synergistic effect on sleep in mice. The duration of non-rapid eye movement (NREM) sleep was significantly prolonged; the number of c-Fos positive neurons increased in the VLPO and decreased in the TMN; the levels of excitatory neurotransmitters were reduced, while the levels of inhibitory neurotransmitters were elevated.

This study reveals that the combination of DMED and ESZ exerts a synergistic effect on sleep in mice. The underlying mechanism may involve the prolongation of NREM sleep, modulation of neuronal activity in the brain regions of VLPO and TMN, as well as alteration in the levels of brain neurotransmitters.

Chart depicting the synergistic effects of combined hypnotic drugs (DMED and ESZ) on sleep in mice. It includes pharmacodynamic and potential mechanistic studies. Pharmacodynamic studies involve isobolographic analysis of subgroups affecting LORR. Mechanistic studies show EEG/EMG recording, c-Fos immunofluorescence in VLPO and TMN, and neurotransmitter level measurement. Conclusions highlight prolonged NREM sleep, altered c-Fos-positive neurons in VLPO and TMN, and changes in neurotransmitter levels.