Abstract Introduction The glymphatic system is a brain-wide clearance pathway responsible for removing metabolic waste products and toxins, functioning primarily during sleep. Among anesthetic agents, dexmedetomidine uniquely promotes slow-wave sleep states, making it particularly relevant for studying sleep-dependent glymphatic clearance. As a commonly used sedative in operating rooms and intensive care units, understanding dexmedetomidine's and other anesthetic-sedatives' specific effects have direct clinical implications. However, nearly all studies have examined dexmedetomidine combined with isoflurane or ketamine, making it unclear which agent is responsible for observed glymphatic effects. Determining independent contributions is critical for optimizing anesthetic selection in clinical practice. To address this gap, we designed a study that separates the individual effects of dexmedetomidine and ketamine on glymphatic function. Methods Male C57BL/6 mice (8-12 weeks, n=4-8 per group) underwent cisterna magna cannulation for intracisternal gadolinium injection during 9.4T MRI under 2 doses of dexmedetomidine (0.2/0.5 mg/kg), isoflurane (1-2%), ketamine (150 mg/kg), or ketamine-dexmedetomidine (75/0.3 mg/kg) anesthesia. Dynamic contrast-enhanced MRI captured tracer distribution over 90 minutes to assess glymphatic function. To quantify parenchymal clearance, separate cohorts received intrastriatal injection of fluorescein-conjugated albumin (74 kDa). Animals then received anesthetic-sedative administration or remained awake (control) before brain harvest at 6, 12, 24 and 48-hour timepoints. Coronal sections (30 μm) were imaged via fluorescence microscopy, and albumin signal intensity was quantified using MATLAB and imageJ. Statistical comparisons used one-way ANOVA with Tukey's post-hoc test. Results Glymphatic function differed significantly between anesthetic groups (p 0.05), with dexmedetomidine (dose dependent effect) demonstrating the greatest enhancement. Comprehensive regional analysis revealed significant group differences across CSF entry sites (basilar artery, basal foramina, Circle of Willis, MCA), intraparenchymal penetration zones (1.5 and 3 mm from MCA), and all major cranial clearance pathways: nasal (olfactory bulb, nasal turbinates, pharyngeal lymphatics), basal ( basal outflow, cranial nerve ganglion), and dorsal (superior sagittal sinus). Ongoing studies using fluorescein–albumin tracers are investigating longer-term parenchymal clearance dynamics across anesthetic groups and awake controls. Conclusion Our study demonstrates that anesthetic choice significantly impacts glymphatic function. Across all major CSF pathways, dexmedetomidine alone produced the greatest enhancement, followed by ketamine-dexmedetomidine combination. Isoflurane and ketamine monotherapy showed the most reduced function. Support (if any)
Algantiry et al. (2026) studied this question.