China
Africa
Explore chapters and articles related to this topic
Adrenoceptors: Classification and Distribution
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
Further roles for imidazoline receptors are now emerging. Imidazolines, such as efaroxan (see Table 5.2), enhance the rate of insulin secretion from the islets of Langerhans, possibly through I2 receptors (Chan et al. 1994). Clonidine and the selective I1 imidazoline agonist, moxonidine (see Table 4.3), inhibit gastric acid secretion and reduce ethanol-induced gastric mucosal injury (Glavin & Smyth 1995). Moxonidine also induces sodium and water excretion when given centrally (Penner & Smyth 1994). However, peripheral administration of the α2-agonists, rilmenidine (I1) and guanabenz (I2), increased blood pressure and urine excretion via α2-adrenoceptors (Evans & Anderson 1995).
Responsiveness of α2-adrenoceptor/I1-imidazoline receptor in the rostral ventrolateral medulla to cardiovascular regulation is enhanced in conscious spontaneously hypertensive rat
Published in Clinical and Experimental Hypertension, 2019
Masanobu Yamazato, Minori Nakamoto, Atsushi Sakima, Yoriko Yamazato, Shuichi Takishita, Yusuke Ohya
Either α2-adrenoceptors (20) or non-adrenergic imidazoline binding site (hypothetical I1-imidazoline receptors) (21) or both (22) may mediate the sympathoinhibitory effect of clonidine and related drugs in the RVLM. However, previous studies (23–25) suggest that the functional dominance of imidazoline receptors in the RVLM I1-receptors has never been cloned or convincingly identified. In contrast, the importance of central α2A-receptors in the action of clonidine was studied in genetically engineered mice expressing mutated α2A-adrenoceptor, but with intact α2B and α2C adrenoceptor subtypes of α2-adrenoceptor; the study showed that impaired α2A-adrenoceptor is sufficient to eliminate the hypotensive effect of clonidine (26). In the present study, the hypotensive and bradycardic effects of clonidine microinjection into RVLM were abolished in WKY rats and significantly attenuated in SHRs with co-injection of 2-methoxyidazoxan—a selective α2-adrenoceptor antagonist. The findings of the present study in conjunction with previous reports (9,26,27) indicate that α2-adrenoceptors in the RVLM contribute to the action of clonidine in the RVLM. Furthermore, the same dose of efaroxan [an α2-antagonist with 40-fold greater affinity for I1-imidazoline receptors (28)] attenuated clonidine-induced hypotension. This finding indicates that I1-imidazoline receptors in the RVLM also contribute to the action of clonidine in the RVLM.
Xylazine poisoning: a systematic review
Published in Clinical Toxicology, 2022
Noah S. Ball, Brittany M. Knable, Taylor A. Relich, Allyson N. Smathers, Michael R. Gionfriddo, Branden D. Nemecek, Courtney A. Montepara, Anthony J. Guarascio, Jordan R. Covvey, David E. Zimmerman
Although not seen in this review, clinicians should obtain an ECG due to the potential for arrhythmias with xylazine. Two patients required a lidocaine infusion at a time when this was standard of practice for the development of premature ventricular contractions; however, this is no longer standard of practice. Administration of atropine is unlikely to have an effect with xylazine toxicity. Similar to clonidine and other imidazolines, xylazine results in alpha-2 agonism and potential agonist activity at the imidazoline receptors, I1 and I2, and not from cholinergic receptors [35–37]. It is still reasonable to administer atropine in presentations with bradycardia and an unknown cause.
The role of selective imidazoline receptor agonists in modern hypertension management: an international real-world survey (STRAIGHT)
Published in Current Medical Research and Opinion, 2020
Markus P. Schlaich, Wael Almahmeed, Samir Arnaout, Dorairaj Prabhakaran, Julia Zhernakova, Nadezhda Zvartau, Aletta E. Schutte
The second generation of centrally acting antihypertensive agents, called selective imidazoline receptor agonists (SIRAs), which are highly selective for the imidazoline I1 receptor while having a low affinity for alpha 2-adrenergic receptors, are also available15,16. Several studies have demonstrated these specific binding properties, with moxonidine showing 10–700-fold greater affinity for I1 receptors compared with alpha 2-adrenergic receptors in the rostral ventrolateral medulla, depending on the study.15–19