In Situ Mass Spectrometry Imaging to Elucidate the Effects of an Adenosine A2A Receptor Agonist and Alprazolam on Sleep Regulation

Alprazolam (Alp), a commonly used sleep medication in clinical practice, has several potential limitations, including a narrow therapeutic dosage range and a delayed sleep onset. CGS21680 (CGS), a selective agonist of the adenosine A_2A receptor, exhibits neuroinhibitory properties. This study aimed to evaluate the effects of CGS on the sleep properties of Alp. The sleep-inducing effects of Alp were assessed through the righting reflex, while the sedative effects of CGS were evaluated by spontaneous activity detection. The synergistic effect of CGS on Alp was evaluated by using electroencephalography and electromyography. The results indicate that we optimized and selected ED₅ dose of Alp and ED₅₀ dose of CGS for coadministration. CGS reduced the sleep latency induced by Alp and extended the sleep duration. The distribution of Alp in the brain was assessed through mass spectrometry imaging (MSI). The blood–brain barrier (BBB) model was established to evaluate the impact of CGS on the transmittance of Alp. The results indicated that CGS influenced the distribution of Alp across various brain regions and increased Alp’s transmittance across the BBB. The metabolic pathways of GABA, glutamate, and glutamine were assessed through MSI and enzyme activity verification. The coadministration of Alp and CGS resulted in the regulation of GABA, glutamate, and glutamine during the sleep latency and sleep maintenance periods, respectively. In conclusion, the potentiating effect of CGS on the sleep-inducing properties of Alp is attributed to its ability to modulate the distribution of Alp in the brain by enhancing BBB permeability and its influence on Alp-induced neurotransmitter release.