Vasoconstriction of porcine left anterior descending coronary artery by ecstasy and cathinone is not an indirect sympathomimetic effect

Ecstasy (3,4-methylenedioxymethamphetamine): Cardiovascular effects and mechanisms

3,4-methylenedioxymethamphetamine or MDMA (known as "ecstasy") is a recreational drug of abuse, popular worldwide for its distinctive psychotropic effects. Currently, the therapeutic potential of MDMA in psychotherapy has attracted a lot of interest from the scientific community, despite the multitude of effects that this drug of abuse elicits on the human body. While neuronal effects have been the most studied, cardiovascular effects have also been described, as increased blood pressure and heart rate are the most recognizable. However, other effects have also been described at the cardiac (impaired cardiac contractile function, arrhythmias, myocardial necrosis and valvular heart disease) and vascular (vasoconstriction, disruption of vascular integrity and altered haemostasis) levels. Several mechanisms have been proposed, from the interaction with monoamine transporters and receptors to the promotion of oxidative stress or the activation of matrix metalloproteinases (MMPs). This review provides an overview of the cardiovascular implications of MDMA intake and underlying mechanisms, relevant when considering its consumption as drug of abuse but also when considering its therapeutic potential in psychiatry. Moreover, the risk/benefit ratio of the therapeutic use of MDMA remains to be fully elucidated from a cardiovascular standpoint, particularly in patients with underlying cardiovascular disease.

Association of Chronic Khat Chewing with Blood Pressure and Predictors of Hypertension Among Adults in Gurage Zone, Southern Ethiopia: A Comparative Study

Purpose

The leaves of the Khat plant contain amphetamine-like compounds which are implicated in the development of hypertension. The increase in blood pressure coincides with the plasma cathinone level. Other factors associated with hypertension are being overweight, obesity, cigarette smoking, alcohol use, physical inactivity, unhealthy diet, and stress. Thus, this study assessed the association of chronic khat chewing with hypertension and other factors associated with hypertension.

Patients and Methods

Acommunity based comparative cross-sectional study was undertaken from October 5, 2018 to February 15, 2019 in Gurage zone, southern Ethiopia. A total of 1200 adults (600 chewers and 600 non-chewers) aged 18 − 65 years were selected using a convenience sampling method. The data was collected by an interviewer-administered questionnaire plus physical measurements and were carried out at a fixed time of the day in the morning (7: 00 am–10:00 am). Linear regression and binary logistic regression analysis were performed to identify the determinant factors of blood pressure. The test of statistically significant association was declared by using 95% CI and p-value less than 0.05.

Results

A total of 1198 adults participated in the study giving a response rate of 99.8%. The mean age of Khat chewers were 34 (± 11.27) and non-chewers were 34.73 (± 11.48) years. The mean values of systolic blood pressure and diastolic blood pressure were higher in chewers than in non-chewers (p < 0.001). The prevalence of diastolic blood pressure > 80mmHg was significantly higher among Khat chewers than in non-chewers (17.4% versus 8.7%, p < 0.001). The duration of Khat chewing was significantly associated with systolic blood pressure (Beta coefficient = 0.83, p < 0.001) and diastolic blood pressure (Beta coefficient = 0.51, p < 0.001). The sex, age, BMI and alcohol were significantly associated with both systolic and diastolic blood pressure.

Conclusion

Chronic Khat chewing, male sex, BMI and alcohol were associated with increased systolic and diastolic blood pressure. To assess the cause and effect relationship between chronic Khat chewing and hypertension further studies with better defined cohorts and basic science studies need to be undertaken.

Possible mechanisms involved in the vasorelaxant effect produced by clobenzorex in aortic segments of rats

Clobenzorex is a metabolic precursor of amphetamine indicated for the treatment of obesity. Amphetamines have been involved with cardiovascular side effects such as hypertension and pulmonary arterial hypertension. The aim of the present study was to investigate whether the direct application of 10^–9–10^–5 M clobenzorex on isolated phenylephrine-precontracted rat aortic rings produces vascular effects, and if so, what mechanisms may be involved. Clobenzorex produced an immediate concentration-dependent vasorelaxant effect at the higher concentrations (10^–7.5–10^–5 M). The present outcome was not modified by 10^–6 M atropine (an antagonist of muscarinic acetylcholine receptors), 3.1×10^–7 M glibenclamide (an ATP-sensitive K⁺ channel blocker), 10^–3 M 4-aminopyridine (4-AP; a voltage-activated K⁺ channel blocker), 10^–5 M indomethacin (a prostaglandin synthesis inhibitor), 10^–5 M clotrimazole (a cytochrome P450 inhibitor) or 10^–5 M cycloheximide (a general protein synthesis inhibitor). Contrarily, the clobenzorex-induced vasorelaxation was significantly attenuated (P<0.05) by 10^–5 M L-NAME (a direct inhibitor of nitric oxide synthase), 10^–7 M ODQ (an inhibitor of nitric oxide-sensitive guanylyl cyclase), 10^–6 M KT 5823 (an inhibitor of protein kinase G), 10^–2 M TEA (a Ca²⁺-activated K⁺ channel blocker and non-specific voltage-activated K⁺ channel blocker) and 10^–7 M apamin plus 10^–7 M charybdotoxin (blockers of small- and large-conductance Ca²⁺-activated K⁺ channels, respectively), and was blocked by 8×10^–2 M potassium (a high concentration) and removal of the vascular endothelium. These results suggest that the direct vasorelaxant effect by clobenzorex on phenylephrine-precontracted rat aortic rings involved stimulation of the NO/cGMP/PKG/Ca²⁺-activated K⁺ channel pathway.

Pharmacological and Toxicological Effects of Catha edulis F. (Khat)

Khat chewing is deeply rooted in the culture and tradition of communities in khat belt countries, and its consumption is spread to other countries through the suitcase trade. The aim of this article is to review current knowledge on the chemistry, social, pharmacology and toxicology of khat and its use. Khat produces effect invariably in every system, which is harmful or beneficial in some instances. Harmful effects are observed in heavy users, although firm evidence is lacking. Chewing khat acutely elicits states of euphoria, which is followed by low mood. Khat contains alkaloids with psychostimulant properties, but the effect cannot be totally explained by these alkaloids. It is also not clear whether the effect produced in some organs like liver could be attributed to khat or pesticides sprayed during farming. Although the evidence indicates that khat has adverse effects in most organs, our understanding of the complex interaction between use and effect is incomplete, and causal relationships have not yet been described. Moreover, khat has positioned itself well in the social, economic and political arena. Thus, a multidisciplinary research is required to understand the different dimensions and come up with ways that maximize the benefit while minimizing the risk. Copyright © 2017 John Wiley & Sons, Ltd.

Methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxypyrovalerone (MDPV) induce differential cytotoxic effects in bovine brain microvessel endothelial cells

Designer drugs such as synthetic psychostimulants are indicative of a worldwide problem of drug abuse and addiction. In addition to methamphetamine (METH), these drugs include 3,4-methylenedioxy-methamphetamine (MDMA) and commercial preparations of synthetic cathinones including 3,4-methylenedioxypyrovalerone (MDPV), typically referred to as "bath salts." These psychostimulants exert neurotoxic effects by altering monoamine systems in the brain. Additionally, METH and MDMA adversely affect the integrity of the blood-brain barrier (BBB): there are no current reports on the effects of MDPV on the BBB. The aim of this study was to compare the effects of METH, MDMA and MDPV on bovine brain microvessel endothelial cells (bBMVECs), an accepted in vitro model of the BBB. Confluent bBMVEC monolayers were treated with METH, MDMA and MDPV (0.5mM-2.5mM) for 24h. METH and MDMA increased lactate dehydrogenase release only at the highest concentration (2.5mM), whereas MDPV induced cytotoxicity at all concentrations. MDMA and METH decreased cellular proliferation only at 2.5mM, with similar effects observed after MDPV exposures starting at 1mM. Only MDPV increased reactive oxygen species production at all concentrations tested whereas all 3 drugs increased nitric oxide production. Morphological analysis revealed different patterns of compound-induced cell damage. METH induced vacuole formation at 1mM and disruption of the monolayer at 2.5mM. MDMA induced disruption of the endothelial monolayer from 1mM without vacuolization. On the other hand, MDPV induced monolayer disruption at doses ≥0.5mM without vacuole formation; at 2.5mM, the few remaining cells lacked endothelial morphology. These data suggest that even though these synthetic psychostimulants alter monoaminergic systems, they each induce BBB toxicity by different mechanisms with MDPV being the most toxic.

Fatal overdose from synthetic cannabinoids and cathinones in Japan: demographics and autopsy findings

BACKGROUND

Sixty-one autopsy cases involving cathinones and/or cannabinoids (synthetic cathinones/cannabinoids) use have been reported. However, little is known about the demographics and autopsy findings in fatal synthetic cathinones/cannabinoids users.

OBJECTIVES

To elucidate demographic and autopsy findings (i.e. major organ pathology and causes of death) in synthetic cathinones/cannabinoids cases.

METHODS

We reviewed forensic autopsy reports in Department of Legal Medicine of Tokyo Women's Medical University (Tokyo, Japan) between 2011 and 2015 (a total of 359). We compared demographic and autopsy findings between synthetic cathinones/cannabinoids and methamphetamine cases (as control subjects).

RESULTS

There were 12 synthetic cathinones/cannabinoids cases and 10 methamphetamine cases. Synthetic cathinones/cannabinoids users were significantly younger than methamphetamine users (p < 0.01), and there were no cases that used both synthetic cathinones/cannabinoids and methamphetamine. Acute intoxication and cardiac ischemia were the two most prominent causes of death in both synthetic cathinones/cannabinoids users and methamphetamine users. Excited delirium syndrome and pulmonary aspiration were found only in synthetic cathinones/cannabinoids cases.

CONCLUSIONS

The populations of synthetic cathinones/cannabinoids and methamphetamine users who died of an overdose are different in Japan. Acute intoxication, cardiac ischemia, excited delirium syndrome, pulmonary aspiration, and drowning are the major autopsy findings in synthetic cathinones/cannabinoids-related death. Clinicians shuld be aware of these potentially fatal complications in the medical management of synthetic cathinones/cannabinoids users.

Contractile effects of 3,4-methylenedioxymethamphetamine on the human internal mammary artery

Since the late 1980s numerous reports have detailed adverse reactions to the use of 3,4-methylenedioxymethamphetamine (MDMA) associated with cardiovascular collapse and sudden death, following ventricular tachycardia and hypertension. For a better understanding of the effects of MDMA on the cardiovascular system, it is critical to determine their effects at the vasculature level, including the transporter or neurotransmitter systems that are most affected at the whole range of drug doses. With this purpose in mind, the aim of our study was to evaluate the contractile effect of MDMA in the human internal mammary artery, the contribution of SERT for this effect and the responsiveness of this artery to 5-HT in the presence of MDMA. We have also studied the possible involvement of 5-HT2 receptors on the MDMA contractile effect in this human blood vessel using ketanserin. Our results showed that MDMA contracted the studied human's internal mammary artery in a SERT-independent form, through activation of 5-HT2A receptors. Considering the high plasma concentrations achieved in heavy users or in situations of acute exposure to drugs, this effect is probably involved in the cardiovascular risk profile of this psychostimulant, especially in subjects with pre-existing cardiovascular disease.

Khat use: history and heart failure

Recent reports suggest that 20 million people worldwide are regularly using khat as a stimulant, even though the habit of chewing khat is known to cause serious health issues. Historical evidence suggests khat use has existed since the 13th century in Ethiopia and the southwestern Arabian regions even before the cultivation and use of coffee. In the past three decades, its availability and use spread all over the world including the United States and Europe. Most of the consumers in the Western world are immigrant groups from Eastern Africa or the Middle East. The global transport and availability of khat has been enhanced by the development of synthetic forms of its active component. The World Health Organization considers khat a drug of abuse since it causes a range of health problems. However, it remains lawful in some countries. Khat use has long been a part of Yemeni culture and is used in virtually every social occasion. The main component of khat is cathinone, which is structurally and functionally similar to amphetamine and cocaine. Several studies have demonstrated that khat chewing has unfavorable cardiovascular effects. The effect on the myocardium could be explained by its effect on the heart rate, blood pressure, its vasomotor effect on the coronary vessels, and its amphetamine-like effects. However, its direct effect on the myocardium needs further elaboration. To date, there are few articles that contribute death among khat chewers to khat-induced heart failure. Further studies are needed to address the risk factors in khat chewers that may explain khat-induced cardiotoxicity, cardiomyopathy, and heart failure.

Why would khat chewers quit? An in-depth, qualitative study on Saudi Khat quitters

Background: Khat chewing, which has many adverse health and social consequences, is highly prevalent and socially accepted in the Jazan region of the Kingdom of Saudi Arabia. Methods: A qualitative study was conducted with 47 adult male former khat users regarding their khat initiation, continuance, and cessation, the amounts of khat they had used, and the health and social consequences of their use and cessation of use. Results: Participants noted a desire to show maturity, ease of availability of khat, and peer pressure as reasons for initiating khat chewing. Many noted long leisure times with little to do as a reason for continuing use. Negative consequences of khat use were seen in economic, health, familial, and sexual areas of their lives. After quitting khat use, participants saw improvements in all of these areas. Conclusions: A comprehensive community development program (CCDP) tackling, among other issues, the normalization of khat use, substantial leisure times with few positive activities, and misinformation about the “benefits” of khat use, as well as developing peer and family training programs to help prevent or stop khat use, would be useful to reduce khat chewing in this community.

Epicardial coronary arteries in khat chewers presenting with myocardial infarction

Background. Khat chewing is a common habit in Yemen despite increased evidence of its negative impact on the cardiovascular system. Aims. We aimed to study the epicardial coronary arteries in khat chewers presenting with myocardial infarction (AMI). Materials and Methods. A descriptive, cross-sectional study was conducted between November 2008 and May 2009 in Yemen. AMI patients who underwent coronary angiogram were enrolled and divided into groups (gp): gp1 (diabetic and khat chewers), gp2 (khat chewers and nondiabetic), and gp3 (diabetic and non-khat users). Results. Of 347 AMI patients 63%, 21%, and 16% were in gp 2, 3, and 1, respectively. Khat chewers were younger in comparison to non-khat users. Group 3 patients were more likely to have multivessel disease, severe left anterior descending (LAD), right coronary artery (RCA) stenosis and total RCA, and left circumflex (Lcx) occlusion compared to other groups. Group 1 patients were more likely to have total LAD occlusion and severe Lcx lesions. In multivariate analysis, age, diabetes mellitus, and smoking were significant independent predictors for significant coronary artery lesions; however, khat chewing did not show such association. Conclusions. Coronary spasm is the main mechanism of AMI in khat chewers. The impact of our finding for risk stratification and management warrants further studies.

'Ecstasy' enhances noise-induced hearing loss

'Ecstasy' or 3,4-methylenedioxy-N-methamphetamine (MDMA) is an amphetamine abused for its euphoric, empathogenic, hallucinatory, and stimulant effects. It is also used to treat certain psychiatric disorders. Common settings for Ecstasy use are nightclubs and "rave" parties where participants consume MDMA and dance to loud music. One concern with the club setting is that exposure to loud sounds can cause permanent sensorineural hearing loss. Another concern is that consumption of MDMA may enhance such hearing loss. Whereas this latter possibility has not been investigated, this study tested the hypothesis that MDMA enhances noise-induced hearing loss (NIHL) by exposing rats to either MDMA, noise trauma, both MDMA and noise, or neither treatment. MDMA was given in a binge pattern of 5 mg/kg per intraperitoneal injections every 2 h for a total of four injections to animals in the two MDMA-treated groups (MDMA-only and Noise + MDMA). Saline injections were given to the animals in the two non-MDMA groups (Control and Noise-only). Following the final injection, noise trauma was induced by a 10 kHz tone at 120 dB SPL for 1 h to animals in the two noise trauma-treated groups (Noise-only and Noise + MDMA). Hearing loss was assessed by the auditory brainstem response (ABR) and cochlear histology. Results showed that MDMA enhanced NIHL compared to Noise-only and that MDMA alone caused no hearing loss. This implies that "clubbers" and "rave-goers" are exacerbating the amount of NIHL when they consume MDMA and listen to loud sounds. In contrast to earlier reports, the present study found that MDMA by itself caused no changes in the click-evoked ABR's wave latencies or amplitudes.

Functional evaluation of the receptors mediating vasoconstriction of rat aorta by trace amines and amphetamines

Trace amines including β-phenylethylamine (β-PEA) and amphetamines classically exert pharmacological actions via indirect sympathomimetic mechanisms. However, there is evidence for other mechanisms and this study explores the receptors mediating vasoconstriction in rat aorta. β-PEA, d-amphetamine, MDMA, cathinone and methylphenidate caused concentration-dependent contractions of rat isolated aortic rings which were unaffected by prazosin (1 μM), ICI-118,551 (1 μM), cocaine (10 μM) and pargyline (10 μM), to inhibit α1- and β2-adrenoceptors, neuronal transport and monoamine oxidase (MAO), respectively. Octopamine concentration-response curves, however, were shifted to the right. In the presence of the inhibitors, the rate of onset of octopamine contractions was slowed. Lineweaver-Burk analysis of the kinetics of the response generated different KM values for octopamine in the absence (2.35 × 10(-6)M) and presence (6.09 × 10(-5)M) of inhibitors, indicating mediation by different receptors. Tryptamine-induced vasoconstriction also resisted blockade by adrenergic inhibitors and the 5-HT1A, 1B, 1D and 5-HT2A receptor antagonists, methiothepin (50 nM) and ketanserin (30 nM), respectively. Trace amines and amphetamines therefore exert vasoconstriction independently of adrenoceptors, neuronal transport and 5-HT receptor activation. There was no evidence of tachyphylaxis or cross-tachyphylaxis of the vasoconstriction to these amines. Tyramine was a partial agonist and in its presence, β-PEA, d-amphetamine and octopamine were antagonised indicating that they all act through a common receptor for which tyramine serves as an antagonist. We conclude that the vasoconstriction is via TAAR-1, because of structural similarities between amines, ability to stimulate recombinant trace amine-associated receptor 1 (TAAR-1) and the presence of TAAR-1 in rat aorta.

Cardiovascular complications of Khat

This article reviews current knowledge in khat (cathinone) research and its health impacts and toxicity in the cardiac system of khat chewers based on current evidence. The authors describe the process by which khat is postulated to induce multiple cardiac abnormalities by illustrating multiple case reports as described from around the world. The role of free radicals in inducing cardiac disease is also discussed. Future research areas are proposed to enhance our understanding of the mode of action of this toxicological drug.

Khat chewing, cardiovascular diseases and other internal medical problems: the current situation and directions for future research

The leaves of khat (Catha edulis Forsk.) are chewed as a social habit for the central stimulant action of their cathinone content. This review summarizes the prevalence of the habit worldwide, the actions, uses, constituents and adverse health effects of khat chewing. There is growing concern about the health hazards of chronic khat chewing and this review concentrates on the adverse effects on health in the peripheral systems of the body, including the cardiovascular system and gastrointestinal tract. Comparisons are made with amphetamine and ecstasy in particular on the detrimental effects on the cardiovascular system. The underlying mechanisms of action of khat and its main constituent, cathinone, on the cardiovascular system are discussed. Links have been proposed between khat chewing and the incidence of myocardial infarction, dilated cardiomyopathy, vascular disease such as hypertension, cerebrovascular ischaemia and thromboembolism, diabetes, sexual dysfunction, duodenal ulcer and hepatitis. The evidence, however, is often based on limited numbers of case reports and only few prospective controlled studies have been undertaken. There is therefore an urgent need for more thorough case-control studies to be performed. This review outlines the current knowledge on the adverse health effects of khat chewing on the cardiovascular system and other internal medical problems, it assesses the evidence and the limitations of the studies and identifies the questions that future studies should address.

Association of khat chewing with increased risk of stroke and death in patients presenting with acute coronary syndrome

OBJECTIVE

To evaluate the prevalence and significance of khat chewing in patients with acute coronary syndrome (ACS).

PATIENTS AND METHODS

From January 29, 2007, through July 29, 2007, 8176 consecutive patients presenting with ACS were enrolled in a prospective, multicenter study from 6 adjacent Middle Eastern countries.

RESULTS

Of the 8176 study patients, 7242 (88.6%) were non-khat chewers, and 934 (11.4%) were khat chewers, mainly of Yemeni origin. Khat chewers were older (57 vs 56 years; P=.01) and more likely to be men (85.7% vs 74.5%) compared with non-khat chewers. Non-khat chewers were more likely to have diabetes mellitus, hypertension, dyslipidemia, obesity, and prior history of coronary artery disease and revascularization. Cigarette smoking was more prevalent in khat chewers, and they were more likely to present greater than 12 hours after onset of symptoms compared with non-khat chewers. At admission, khat chewers had higher heart rate, Killip class, and Global Registry of Acute Coronary Events risk scores. Khat chewers had a significantly higher risk of cardiogenic shock, stroke, and mortality. After adjustment of baseline variables, khat chewing was an independent risk factor for in-hospital mortality (odds ratio, 1.9; 95% confidence interval, 1.3-2.7; P<.001) and stroke (odds ratio, 2.7; 95% confidence interval, 1.3-5.9; P=.01).

CONCLUSION

In this large cohort of patients with ACS, khat chewing was prevalent and was associated with increased risk of stroke and death. In the context of increasing global migration, a greater awareness of potential widespread practices is essential.

Case report of ecstasy-induced renal venous thrombosis

The use of 3,4-methylenedioxymethamphetamine, also known as MDMA or ecstasy, has been associated with vascular and end-organ damage. This case report describes, with histological evidence, the development renal venous thrombosis presenting with acute kidney injury following oral ingestion of 3,4-methylenedioxymethamphetamine (ecstasy).

Effects of dietary amines on the gut and its vasculature

Trace amines, including tyramine and β-phenylethylamine (β-PEA), are constituents of many foods including chocolate, cheeses and wines and are generated by so-called ‘friendly’ bacteria such as Lactobacillus, Lactococcus and Enterococcus species, which are found in probiotics. We therefore examined whether these dietary amines could exert pharmacological effects on the gut and its vasculature. In the present study we examined the effects of tyramine and β-PEA on the contractile activity of guinea-pig and rat ileum and upon the isolated mesenteric vasculature and other blood vessels. Traditionally, these amines are regarded as sympathomimetic amines, exerting effects through the release of noradrenaline from sympathetic nerve endings, which should relax the gut. A secondary aim was therefore to confirm this mechanism of action. However, contractile effects were observed in the gut and these were independent of noradrenaline, acetylcholine, histamine and serotonin receptors. They were therefore probably due to the recently described trace amine-associated receptors. These amines relaxed the mesenteric vasculature. In contrast, the aorta and coronary arteries were constricted, a response that was also independent of a sympathomimetic action. From these results, we propose that after ingestion, trace amines could stimulate the gut and improve intestinal blood flow. Restriction of blood flow elsewhere diverts blood to the gut to aid digestion. Thus, trace amines in the diet may promote the digestive process through stimulation of the gut and improved gastrointestinal circulation.

Dietary trace amine-dependent vasoconstriction in porcine coronary artery

BACKGROUND AND PURPOSE

The dietary trace amines tyramine and beta-phenylethylamine (beta-PEA) can increase blood pressure. However, the mechanisms involved in the vascular effect of trace amines have not been fully established. The purpose of this study was to evaluate whether trace amine-dependent vasoconstriction was brought about by tyramine and beta-PEA acting as indirect sympathomimetic agents, as previously assumed, or whether trace amine-dependent vasoconstriction could be mediated by recently discovered trace amine-associated (TAA) receptors.

EXPERIMENTAL APPROACH

The responses to p-tyramine and beta-PEA were investigated in vitro in rings of the left anterior descending coronary arteries of pigs.

KEY RESULTS

p-Tyramine induced a concentration-dependent (0.1-3 mM) vasoconstriction. The maximum response and pD(2) value for p-tyramine was unaffected by endothelium removal or pre-treatment with antagonists for adrenoceptors, histamine, dopamine or 5-HT receptors. beta-PEA also produced a concentration-dependent (0.3-10 mM) vasoconstriction which was unaffected by endothelium removal, beta-adrenoceptor or 5-HT receptor antagonists. A substantial, but reduced, response to beta-PEA was obtained in the presence of prazosin (alpha(1)-adrenoceptor antagonist), haloperidol (D(2)/D(3) dopamine receptor antagonist) or mepyramine (H(1) histamine receptor antagonist). The pD(2) value for beta-PEA was unaffected by any of the antagonists tested.

CONCLUSIONS AND IMPLICATIONS

Vasoconstriction induced by p-tyramine does not involve an indirect sympathomimetic effect, although vasoconstriction caused by beta-PEA may occur, in part, by this mechanism. We therefore propose that trace amine-dependent vasoconstriction is mediated by phenylethylamine-specific receptors, which are closely related to or identical to TAA receptors. These receptors could provide a target for new antihypertensive therapies.