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The cardiac Mg2+-sensitive, TRPM6, and TRPM7-like channels remain undefined, especially with the uncertainty regarding TRPM6 expression in cardiomyocytes. Additionally, their contribution to the cardiac action potential (AP) profile is unclear. Immunofluorescence assays showed the expression of the TRPM6 and TRPM7 proteins in isolated pig atrial and ventricular cardiomyocytes, of which the expression was modulated by incubation in extracellular divalent cation-free conditions. In patch clamp studies of cells dialyzed with solutions containing zero intracellular Mg2+ concentration ([Mg2+]i) to activate the Mg2+-sensitive channels, raising extracellular [Mg2+] ([Mg2+]o) from the 0.9-mM baseline to 7.2 mM prolonged the AP duration (APD). In contrast, no such effect was observed in cells dialyzed with physiological [Mg2+]i. Under voltage clamp, in cells dialyzed with zero [Mg2+]i, depolarizing ramps induced an outward-rectifying current, which was suppressed by raising [Mg2+]o and was absent in cells dialyzed with physiological [Mg2+]i. In cells dialyzed with physiological [Mg2+]i, raising [Mg2+]o decreased the L-type Ca2+ current and the total delayed-rectifier current but had no effect on the APD. These results suggest a co-expression of the TRPM6 and TRPM7 proteins in cardiomyocytes, which are therefore the molecular candidates for the native cardiac Mg2+-sensitive channels, and also suggest that the cardiac Mg2+-sensitive current shortens the APD, with potential implications in arrhythmogenesis.

Channelopathies represent diseases caused by mutations in the genes encoding ion channels or associated proteins. With the advent of novel electrophysiology and molecular biology techniques, a wide variety of ion channels have been identifi ed in different regions of the working myocardium or conduction system, and their biophysical and pharmacological properties, as well as involvement in different pathophysiology processes, are thoroughly characterized. This wealth of knowledge offers a better understanding of the intricate chemical and electrical events underlying a large class of rare heart diseases, most of them associated with arrhythmias, and also reveals novel mechanisms in the most frequent cardiovascular diseases and their complications. Within the present chapter we tackled the challenging task of presenting a comprehensive review of this rapidly expanding domain, with the hope of rendering relevant information for specialists with an interest in this highly exciting fi eld of research.

Retinal migraine is usually defined by transitory attacks of fully reversible monocular visual loss, mostly with aura. An accurate diagnostic can be completed based upon the International Classification of Headache Disorders-2 (ICHD-2) criteria. In view of this, we summarized some clinical features, treatment principles, complications, prognosis and prophylaxis.

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