Melatonin and its analogs potentiate the nifedipine‐sensitive high‐voltage‐activated calcium current in the chick embryonic heart cells

Abstract

Effects of melatonin and its analogs on the voltage-activated calcium current of embryonic chick ventricular cardiomyocytes were investigated. Myocytes were dissociated from 14- to 16-day-old chicks (yellow Red Rob) embryonic hearts and cultured for 2 3 days. Calcium currents were studied by the patch-clamp technique. Whole-cell current recording showed nifedipine-sensitive, high-voltage-activated L-type calcium current inactivated in 70-100 ms during the voltage step period of 200 ms. There was no evidence of low-voltage-activated T-type calcium channels. Melatonin (ejected solution: 50 micromol/L melatonin; concentration at the vicinity of recording cell: about 1-5 micromol/L melatonin) and its analogs, 2-iodomelatonin and 2-iodo-n-butanol-5-methoxytryptamine, significantly increased the amplitude of the calcium current by 42-62%. The effect of melatonin on the L-type calcium current was not desensitised by repeated melatonin treatment. Our results suggest a specific melatonin receptor-mediated action on the calcium channel of the embryonic chick myocyte. The melatonin-induced increase in high-voltage calcium current may increase myocyte contractility and enhance cardiac output. A regulatory role of melatonin on the chick cardiac function should be further considered.

Stimulation of Melatonin Receptors Decreases Calcium Levels in Xenopus Tectal Cells by Activating GABAC Receptors

“…Several studies indicate that the effects of melatonin on calcium accumulation include a downstream influence on calcium influx through calcium channels (Ayar et al 2001;Mei et al 2001;Vanecek and Klein 1995). Our results suggest that in tectal cells, melatonin regulates calcium increases by an action involving an inhibitory Gprotein and GABA receptors.…”

The melatonin receptor subtype MT2 is present in the human cardiovascular system

“…In this study we were interested whether the MT 2 ‐receptor is expressed in human coronary arteries and aorta, as it was repeatedly postulated that this receptor subtype is expressed and is functional in rat arteries [4, 8–10]. Furthermore, we also investigated the MT 2 expression in left ventricular specimens, because previous binding studies suggested that melatonin receptors are present in hearts of birds and other animals [11], and the ability of melatonin to modulate calcium channels of chick cardiomyocytes in vitro [12] suggests that this effect is also receptor‐mediated. A final aim of this project was to compare expression levels for the MT 2 receptor mRNA in healthy and diseased specimens (aorta, left ventricle and coronary arteria), which were derived from healthy heart donors or from patients with ischemic or dilated cardiomyopathy, respectively.…”

Selective estrogen receptor modulation prevents scoliotic curve progression: radiologic and histomorphometric study on a bipedal C57Bl6 mice model

“…proprioceptive systems, biomechanical factors, uncoupled neuro-osseous growth and dissociation between the timing of skeletal and CNS maturation [1][2][3][4][5][6][7]. There is considerable difficulty in distinguishing the primary underlying pathogenetic factor(s) that cause deformity from the secondary changes that arise secondary to the deformity.…”