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Synapses
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The binding of GABA to GABAB receptors in the presynaptic terminal can also cause the Gβγ subunit of a G protein to close voltage-gated Ca2+ channels and open K+ channels. This reduces the influx of Ca2+ and enhances repolarization of the presynaptic terminal, thereby reducing the width of the presynaptic AP. Both of these effects decrease transmitter release. Another effect of the Gβγ subunit is believed to be a reduction in efficacy of Ca2+ to cause fusion of the vesicle membrane with the membrane of the presynaptic terminal. These, however, are slower processes compared to the ionotropic effect on GABAA receptors.
β2-Agonists: Terbutaline, Albuterol, and Fenoterol GüNther Hochhaus and Helmut MöLlmann
Published in Hartmut Derendorf, Günther Hochhaus, Handbook of Pharmacokinetic/Pharmacodynamic Correlation, 2019
Hartmut Derendorf, Günther Hochhaus
The most dominant side effect of β-agonists is a tremor of the skeleton muscles, most visible in the hand regions. This effect is mediated through β2-receptors. The increase in heart rate is induced by both a β1-receptor-mediated positive ionotropic effect and an increase in cardiac output. In addition, a β2-receptor-related peripheral vasodilatation stimulates the cardiac system by a reflexogenic mechanism (Table 2). Glycogenolysis, gluconeogenesis, insulin secretion, and potassium uptake into skeletal muscles are also β2-adrenoceptor-mediated effects. These are seen after parental and oral administration of β2-agonists, but also after high inhalation doses.
Accident and Emergency
Published in Nagi Giumma Barakat, Get Through, 2006
The ionotropic effect of digitalis is usually brought about by binding to and inhibiting the Na+/K+ ATPase that maintains high Na+ in myocardial cells. This will make Ca2+ available for contraction. Digitalis increases the sensitivity of the arterial baroreceptor reflex, resulting in an increase in vagal and a decrease in sympathetic efferent activity, which reduces the resting heart rate. Digitalis sensitivity is enhanced by hypokalaemia, hypomagnesaemia, hypocal-caemia and hyponatraemia. Hyperthyroidism will accelerate its half-life. Some antacids and neomycin will reduce its absorption. SVT and VT are less common following digitalis toxicity.
Effects of pinealectomy and crocin treatment on rats with isoproterenol-induced myocardial infarction
Published in Drug and Chemical Toxicology, 2022
Mehmet Demir, Eyup Altinoz, Hulya Elbe, Yasemin Bicer, Gurkan Yigitturk, Melike Karayakali, Arwa Fadıl Haqi Ballur
Increases in cardiac troponin T (cTnT), troponin I (cTnI), creatine kinase MB isoenzyme (CK-MB), lactate dehydrogenase (LDH), and several other proteins released into the blood by damaged myocytes evidence the presence of MI (O'brien et al. 2006). Catecholamines have a positive ionotropic effect at low concentrations and play a regulatory role in heart functions. However, at high doses (endogenous or exogenous), they may induce structural and biochemical changes that lead to irreversible damages by exhausting reserve energy in cardiomyocytes (Sushamakumari et al. 1989).
Ultrahigh verapamil-loaded controlled release polymeric beads using superamphiphobic substrate: D-optimal statistical design, in vitro and in vivo performance
Published in Drug Delivery, 2018
Carol Yousry, Maha M. Amin, Ahmed H. Elshafeey, Omaima N. El Gazayerly
Verapamil hydrochloride (VP) is one of the widely used calcium channel blocker in the pharmaceutical market (Yassin et al., 2006). It is effectively used as an antiarrhythmic agent to control tachyarrhythmias. Its potent vasodilating and negative ionotropic effect supports myocardial infarction and cardiomyopathy treatment (Choi & Burm, 2005).