Further analysis of the inhibition by agmatine on the cardiac sympathetic outflow: Role of the α2-adrenoceptor subtypes

Mitigating effects of agmatine on myocardial infarction in rats subjected to isoproterenol

Isoproterenol (ISO) usage is limited by its potential for cardiotoxicity. We sought to investigate the potential of agmatine in mitigating ISO-induced cardiotoxicity. Agmatine (100 mg/kg/day) was intraperitoneally administered to Wistar rats for 7 days in the presence or absence of cardiotoxicity induced by subcutaneous injection of ISO (85 mg/kg) on the sixth and seventh days. ECG parameters, lactate dehydrogenase (LDH), malondialdehyde (MDA), and creatinine phosphokinase (CPK) were investigated. Changes in cardiac tissue were also investigated using H&E staining. The heart weight/body weight ratio increased in ISO-treated rats. In the agmatine + ISO group, the increased heart rate observed in ISO-treated rats was reversed (317.2 ± 10.5 vs 452.2 ± 10.61, P < 0.001). Agmatine ameliorated the change in PR, RR, and ST intervals and the QRS complex, which was reduced by ISO. Treatment with saline, ISO, and agmatine had no significant effect on papillary muscle stimulation (P > 0.05). The administration of agmatine to ISO-receiving group could mitigate several parameters when compared to ISO-receiving group including increasing papillary muscle contraction (0.83 vs 0.71 N/M2 respectively, P < 0.01), decreasing LDH levels (660 ng/ml vs 1080 ng/ml, respectively, P < 0.05), decreasing CPK levels (377 U/l vs 642 U/l, respectively, P < 0.05) and decreasing MDA levels (20.32 µM/l vs 46.83 µM/l, P < 0.001). Coadministration of agmatine and ISO is capable of ameliorating ISO cardiotoxicity by antioxidant effects and controlling the hemostasis of calcium in myocytes.

Pharmacological profile of agmatine: An in-depth overview

Agmatine, a naturally occurring polyamine derived from arginine via arginine decarboxylase, has been shown to play multifaceted roles in the mammalian body, impacting a wide range of physiological and pathological processes. This comprehensive review delineates the significant insights into agmatine's pharmacological profile, emphasizing its structure and metabolism, neurotransmission and regulation, and pharmacokinetics and function. Agmatine's biosynthesis is highly conserved across species, highlighting its fundamental role in cellular functions. In the brain, comparable to established neurotransmitters, agmatine acts as a neuromodulator, influencing the regulation, metabolism, and reabsorption of neurotransmitters that are key to mood disorders, learning, cognition, and the management of anxiety and depression. Beyond its neuromodulatory functions, agmatine exhibits protective effects across various cellular and systemic contexts, including neuroprotection, nephroprotection, cardioprotection, and cytoprotection, suggesting a broad therapeutic potential. The review explores agmatine's interaction with multiple receptor systems, including NMDA, α2-adrenoceptors, and imidazoline receptors, elucidating its role in enhancing cell viability, neuronal protection, and synaptic plasticity. Such interactions underpin agmatine's potential in treating neurological diseases and mood disorders, among other conditions. Furthermore, agmatine's pharmacokinetics, including its absorption, distribution, metabolism, and excretion, are discussed, underlining the complexity of its action and the potential for therapeutic application. The safety and efficacy of agmatine supplementation, demonstrated through various animal and human studies, affirm its potential as a beneficial therapeutic agent. Conclusively, the diverse physiological and therapeutic effects of agmatine, spanning neurotransmission, protection against cellular damage, and modulation of various receptor pathways, position it as a promising candidate for further research and clinical application. This review underscores the imperative for continued exploration into agmatine's mechanisms of action and its potential in pharmacology and medicine, promising advances in the treatment of numerous conditions.

Cardiovascular Effects Mediated by Imidazoline Drugs: An Update

OBJECTIVE

Clonidine is a centrally acting antihypertensive drug. Hypotensive effect of clonidine is mediated mainly by central α2-adrenoceptors and/or imidazoline receptors located in a complex network of the brainstem. Unfortunately, clonidine produces side effects such as sedation, mouth dry, and depression. Moxonidine and rilmenidine, compounds of the second generation of imidazoline drugs, with fewer side effects, display a higher affinity for the imidazoline receptors compared with α2-adrenoceptors. The antihypertensive action of these drugs is due to inhibition of the sympathetic outflow primarily through central I1-imidazoline receptors in the RVLM, although others anatomical sites and mechanisms/receptors are involved. Agmatine is regarded as the endogenous ligand for imidazoline receptors. This amine modulates the cardiovascular function. Indeed, when administered in the RVLM mimics the hypotension of clonidine.

RESULTS

Recent findings have shown that imidazoline drugs also exert biological response directly on the cardiovascular tissues, which can contribute to their antihypertensive response. Currently, new imidazoline receptors ligands are in development.

CONCLUSION

In the present review, we provide a brief update on the cardiovascular effects of clonidine, moxonidine, rilmenidine, and the novel imidazoline agents since representing an important therapeutic target for some cardiovascular diseases.