Cardiorespiratory Anomalies in Mice Lacking CB₁ Cannabinoid Receptors

<div><p>Cannabinoid type 1 (CB₁) receptors are expressed in the nervous and cardiovascular systems. In mice, CB₁ receptor deficiency protects from metabolic consequences of a high-fat diet (HFD), increases sympathetic activity to brown fat, and entails sleep anomalies. We investigated whether sleep-wake and diet-dependent cardiorespiratory control is altered in mice lacking CB₁ receptors. CB₁ receptor knock-out (KO) and intact wild-type (WT) mice were fed standard diet or a HFD for 3 months, and implanted with a telemetric arterial pressure transducer and electrodes for sleep scoring. Sleep state was assessed together with arterial pressure and heart rate (home cage), or breathing (whole-body plethysmograph). Increases in arterial pressure and heart rate on passing from the light (rest) to the dark (activity) period in the KO were significantly enhanced compared with the WT. These increases were unaffected by cardiac (β₁) or vascular (α₁) adrenergic blockade. The breathing rhythm of the KO during sleep was also more irregular than that of the WT. A HFD increased heart rate, impaired cardiac vagal modulation, and blunted the central autonomic cardiac control during sleep. A HFD also decreased cardiac baroreflex sensitivity in the KO but not in the WT. In conclusion, we performed the first systematic study of cardiovascular function in CB₁ receptor deficient mice during spontaneous wake-sleep behavior, and demonstrated that CB₁ receptor KO alters cardiorespiratory control particularly in the presence of a HFD. The CB₁ receptor signaling may thus play a role in physiological cardiorespiratory regulation and protect from some adverse cardiovascular consequences of a HFD.</p>