OPHTHALMOLOGIC MANIFESTATIONS IN MELAS SYNDROME

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Title:	OPHTHALMOLOGIC MANIFESTATIONS IN MELAS SYNDROME
Authors:	FANG, W;HUANG, CC;LEE, CC;CHENG, SY;PANG, CY;WEI, YH
Contributors:	附設醫院神經部;CHANG GUNG MEM HOSP,CHANG GUNG MED COLL,DEPT NEUROL,199 TUNG HWA N RD,TAIPEI,TAIWAN;CHINA MED COLL HOSP,DEPT NEUROL,TAICHUNG,TAIWAN;NATL YANG MING MED COLL,DEPT BIOCHEM,TAIPEI,TAIWAN
Date:	1993
Issue Date:	2010-09-24 14:43:13 (UTC+8)
Publisher:	AMER MEDICAL ASSOC
Abstract:	1 The pharmacological and electrophysiological effect of 2-phenyl-4-oxo-hydroquinoline (YT-1), a new synthetic agent, were determined in rat isolated cardiac tissues and ventricular myocytes. 2 YT-1 was found to have a positive inotropic effect in both atria and ventricular muscles but did not cause significant increases in the spontaneously beating rate of right atria. 3 The positive inotropic effect of YT-1 was antagonized neither by beta-nor by alpha-adrenoceptor antagonists but was partially antagonized by a Ca2+ channel blocker (verapamil) and a K+ channel blocker (4-AP). 4 The action potential duration and amplitude of ventricular cells were progressively increased as the concentration of YT-1 was increased from 3 to 30 mum. 5 A voltage clamp study revealed that the prolongation of action potential duration by YT-1 was associated with a prominent inhibition of 4-AP-sensitive transient outward current (I(to)). At potentials negative to the reversal potential of Kl-channels, the inward current through these channels was partially reduced by YT-1. At potentials positive to the reversal potential, the outward current through these channels was affected very little. 6 Although YT-1 blocked the amplitude of I(to), the voltage-dependence of the steady-state inactivation of I(to), was unaffected. 7 Apart from the inhibition of K+ currents, YT-1 also inhibited the sodium inward current. 8 The evidence suggests that YT-1 increases the slow inward Ca2+ current (I(Ca)) significantly. 9 It is concluded that the positive inotropic effect of YT-1 is due predominantly to the increase of I(Ca) and inhibition of I(to).
Relation:	ARCHIVES OF NEUROLOGY 50(9):977-980
Appears in Collections:	[China Medical University Hospital] Jurnal articles

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