DMSO potentiates the suppressive effect of dronabinol, a cannabinoid, on sleep apnea and REM sleep

PurposeDimethyl sulfoxide (DMSO) is an amphipathic molecule with innate biological activity that also is used to dissolve both polar and nonpolar compounds in preclinical and clinical studies. Recent investigations of dronabinol, a cannabinoid, dissolved in DMSO demonstrated decreased sleep apnea frequency and time spent in REM sleep in rats. Here, we tested the effects of dronabinol dissolved in 25% DMSO (diluted in phosphate-buffered saline) to rule out potentiating effects of DMSO.\n\nMethodsSprague-Dawley rats were anesthetized and implanted with bilateral stainless steel screws into the skull for electroencephalogram recording and bilateral wire electrodes into the nuchal muscles for electromyogram recording. Each animal was recorded by polysomnography. The study was a fully nested, repeated measures crossover design, such that each rat was recorded following each of 8 intraperitoneal injections separated by three days: vehicle (25% DMSO/PBS); vehicle and CB1 antagonist (AM 251); vehicle and CB2 antagonist (AM 630); vehicle and CB1/CB2 antagonist; dronabinol (CB1/CB2 agonist); dronabinol and CB1 antagonist; dronabinol and CB2 antagonist; and dronabinol and CB1/CB2 antagonist. Sleep was manually scored into NREM and REM stages, and apneas were quantified.\n\nResultsDronabinol dissolved in 25% DMSO did not suppress apnea or modify sleep efficiency compared to vehicle controls, in contrast to previously published results. However, dronabinol did suppress REM sleep, which is in line with previously published results.\n\nConclusionsDronabinol in 25% DMSO partially potentiated dronabinols effects, suggesting a concomitant biological effect of DMSO on breathing during sleep.