Abstract 13228: Cannabis Inhalation Reduces Muscle Sympathetic Nerve Activity in Humans

Abstract

Introduction: Despite widespread use, the neuro-cardiovascular responses associated with cannabis use remain incompletely understood. Acute increases in heart rate, which are abolished under beta-adrenoreceptor blockade, suggest cannabis increases cardiac sympathetic activity; however, its effects on peripheral sympathetic outflow have not been measured. The objective of this work was to quantify direct recordings of efferent post-ganglionic muscle sympathetic nerve activity (MSNA) following cannabis inhalation. Hypothesis: MSNA would be increased following cannabis inhalation. Methods: Blood pressure (BP), heart rate, and MSNA measured from the fibular nerve, were recorded in seventeen young, healthy participants (22±3y: 8F) for a 10-minute epoch before and after inhalation of aerosolized dry cannabis flower (100mg, 13.6% THC). Cardiac output was estimated from finger photoplethysmography (Modelflow method). Arterial baroreflex control of MSNA was quantified using the slope of the weighted linear regression between diastolic BP and MSNA. Results: Mean BP (79±7 vs. 84±8mmHg), heart rate (61±7 vs. 81±14bpm), cardiac output (4.8±1.1 vs. 6.8±2.5L/min), and total vascular conductance (50±11 vs. 71±26mL/min/mmHg) were increased, while MSNA burst frequency (17±7 vs. 8±6bursts/min), incidence (29±11 vs. 11±9bursts/100hb), and amplitude (38.6±6.4% vs. 23.8±8.3%), and sympathetic baroreflex sensitivity (-3.9±1.8 vs. -1.5±1.5bursts/100hb/mmHg) were decreased following cannabis inhalation (all P <0.01). The rise in cardiac output was negatively associated with the reduction in MSNA burst frequency (r 2 =0.40; P <0.01). Conclusions: These data demonstrate that MSNA is reduced following acute cannabis inhalation in humans and is mediated, in part, through a baroreflex mechanism.