Do cannabinoids exhibit a tyramine-like effect?

Why Do Marijuana and Synthetic Cannabimimetics Induce Acute Myocardial Infarction in Healthy Young People?

The use of cannabis preparations has steadily increased. Although cannabis was traditionally assumed to only have mild vegetative side effects, it has become evident in recent years that severe cardiovascular complications can occur. Cannabis use has recently even been added to the risk factors for myocardial infarction. This review is dedicated to pathogenetic factors contributing to cannabis-related myocardial infarction. Tachycardia is highly important in this respect, and we provide evidence that activation of CB₁ receptors in brain regions important for cardiovascular regulation and of presynaptic CB₁ receptors on sympathetic and/or parasympathetic nerve fibers are involved. The prototypical factors for myocardial infarction, i.e., thrombus formation and coronary constriction, have also been considered, but there is little evidence that they play a decisive role. On the other hand, an increase in the formation of carboxyhemoglobin, impaired mitochondrial respiration, cardiotoxic reactions and tachyarrhythmias associated with the increased sympathetic tone are factors possibly intensifying myocardial infarction. A particularly important factor is that cannabis use is frequently accompanied by tobacco smoking. In conclusion, additional research is warranted to decipher the mechanisms involved, since cannabis use is being legalized increasingly and Δ⁹-tetrahydrocannabinol and its synthetic analogue nabilone are indicated for the treatment of various disease states.

Cannabidiol Affects the Bezold-Jarisch Reflex via TRPV1 and 5-HT3 Receptors and Has Peripheral Sympathomimetic Effects in Spontaneously Hypertensive and Normotensive Rats

Cannabidiol (CBD) is a nonpsychotropic constituent of Cannabis sativa L. It is suggested to be useful in hypertension. Under in vitro conditions, it activates vanilloid TRPV1 and inhibits serotonin 5-HT3 receptors, i.e., receptors involved in the Bezold-Jarisch reflex stimulation. The aim of our study was to compare the cardiovascular effects of CBD in spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats. Experiments were performed on conscious, urethane-anesthetized, and pithed rats. In pithed SHR and WKY, CBD increased heart rate (HR) and systolic blood pressure (SBP) and decreased diastolic BP (DBP) in a manner insensitive to adrenalectomy. Propranolol strongly impaired the CBD-induced increases in HR and SBP without affecting the decreases in DBP. Desipramine also reduced the CBD-induced effects on HR and SBP and further increased its effects on DBP. In anesthetized rats, bolus i.v. injection of single doses of CBD induced short-lasting decreases in HR, SBP, and DBP, stronger in SHR than in WKY and prevented by bilateral vagotomy. The CBD-induced fall in HR but not in BP was diminished by the TRPV1 receptor antagonist capsazepine and almost completely abolished if CBD was re-injected after previous administration. CBD reduced the Bezold-Jarisch reflex elicited by the 5-HT3 receptor agonist phenylbiguanide but not that evoked by the TRPV1 agonist capsaicin. In conscious rats, CBD did not affect cardiovascular parameters. In isolated left atria, CBD decreased contractile force. Conclusions: Cannabidiol (1) induces the Bezold-Jarisch reflex likely via TRPV1 receptors (which undergo tachyphylaxis) more markedly in SHR than in WKY; (2) inhibits the Bezold-Jarisch reflex induced by activation of 5-HT3 but not TRPV1 receptors; (3) has peripheral sympathomimetic, (4) vasodilatory, and (5) negative inotropic effects. The above properties of CBD should be taken under consideration when CBD is used for therapeutic purposes.

Do cannabinoids exhibit a tyramine-like effect?

The major constituent of the cannabis plant, Δ(9)-tetrahydrocannabinol, has stimulatory and depressant effects on cardiovascular functions. There is evidence from an in vivo study on the urethane-anaesthetized rat that part of the stimulatory effects is related to a tyramine-like activity. In the present study, we examined whether Δ(9)-tetrahydrocannabinol induces carrier-mediated noradrenaline release in vitro. The study was extended to another phytocannabinoid, cannabidiol, to the synthetic cannabinoids CP 55,940 and WIN 55,212-2 and to the endocannabinoids anandamide and 2-arachidonoyl glycerol. Tissue pieces of the renal cortex from the mouse and the rat were preincubated with (3)H-noradrenaline and superfused. The effect of the cannabinoids on basal (3)H-noradrenaline release was studied. Tyramine served as a positive control. In the mouse kidney, basal (3)H-noradrenaline release was increased by tyramine 0.1, 1 and 10 μM by 39, 91 and 212 %, respectively, and, in the rat kidney, (3)H-noradrenaline release was increased by tyramine 10 μM by 158 %. All effects were abolished by desipramine 1 μM, an inhibitor of the neuronal noradrenaline transporter. The cannabinoids at 0.1, 1 and 10 μM (CP 55,940 at 0.1, 1 and 3.2 μM) did not affect (3)H-noradrenaline release in the mouse kidney. The highest concentration of the cannabinoids (10 μM and in the case of CP 55,940 3.2 μM) also failed to affect (3)H-noradrenaline release in the rat kidney. In conclusion, the cannabinoids Δ(9)-tetrahydrocannabinol, cannabidiol, CP 55,940, WIN 55,212-2, anandamide and 2-arachidonoyl glycerol do not possess a tyramine-like effect on noradrenaline release.