The exchange factor directly activated by cAMP (Epac) is a newly discovered direct target for cAMP and a guanine-nucleotide exchange factor for the small GTPase Rap. Little is known about the neuronal functions of Epac. Here we show that activation of Epac by specific cAMP analogs or by the pituitary adenylate cyclaseactivating polypeptide induces a potent activation of the Ca 2؉ -sensitive big K ؉ channel, slight membrane hyperpolarization, and increased after-hyperpolarization in cultured cerebellar granule cells. These effects involve activation of Rap and p38 MAPK, which mobilizes intracellular Ca 2؉ stores. These findings reveal a cAMP Epac-dependent and protein kinase A-independent signaling cascade that controls neuronal excitability.excitability ͉ granule cells ͉ mouse ͉ calcium ͉ PACAP

Aldosterone modulates the expression of cardiac voltage-operated Ca2+ channels and accelerates beating in cultured neonatal rat ventricular myocytes. This chronotropic action of aldosterone appears to be linked to increased T channel activity and could contribute to the deleterious effect of an excess of this steroid in vivo on cardiac function.

HF-1 b, an SP1 -related transcription factor, is preferentially expressed in the cardiac conduction system and ventricular myocytes in the heart. Mice deficient for HF-1 b survive to term and exhibit normal cardiac structure and function but display sudden cardiac death and a complete penetrance of conduction system defects, including spontaneous ventricular tachycardia and a high incidence of AV block. Continuous electrocardiographic recordings clearly documented cardiac arrhythmogenesis as the cause of death. Single-cell analysis revealed an anatomic substrate for arrhythmogenesis, including a decrease and mislocalization of connexins and a marked increase in action potential heterogeneity. Two independent markers reveal defects in the formation of ventricular Purkinje fibers. These studies identify a novel genetic pathway for sudden cardiac death via defects in the transition between ventricular and conduction system cell lineages.

Background-Reperfusion during acute myocardial infarction remains the best treatment for reducing infarct size.Postconditioning, applied at the onset of reperfusion, reduces myocardial infarction both in animals and humans. The objective of this study was to identify the time delay to apply postconditioning at reperfusion, allowing preservation of cardioprotection in the mouse myocardium. This is a major issue in the management of acute myocardial infarction patients. Methods and Results-Mice were subjected to 40 minutes of ischemia and 60 minutes of reperfusion (IR 60Ј ).Postconditioning protocols corresponding to repetitive ischemia (3 cycles of 1 minute of ischemia and 1 minute of reperfusion) were applied during early reperfusion at various time durations (⌬t) after reopening of the coronary artery (⌬tϭ10 seconds, 1,5,10,15,20, 30, and 45 minutes; PostC ⌬t ). Infarct size/area at risk was reduced by 71% in PostC ⌬1 compared with IR 60Ј mice (Pϭ5ϫ10 Ϫ6 ). There was a linear correlation (r 2 ϭ0.91) between infarct size and ⌬t, indicating that the cardioprotective effect of delayed postconditioning was progressively attenuated when ⌬t time increased. The protective effect of PostC ⌬1 and PostC ⌬15 was still effective when the duration of reperfusion was prolonged to 24 hours (IR 24 hours ; PostC ⌬1 and PostC ⌬15 versus IR 24 hours , Pϭ0.001). Similar results were obtained for internucleosomal DNA fragmentation and lactate dehydrogenase release. Key Words: apoptosis Ⅲ ischemia Ⅲ myocardial infarction Ⅲ postconditioning Ⅲ reperfusion injury A cute myocardial infarction is a major cause of heart failure and death. Rapid reperfusion of the ischemic myocardium, by either thrombolysis or primary percutaneous coronary intervention, remains the best treatment for attenuating myocardial infarction. However, reperfusion itself has the potential to initiate additional lethal injury. This deleterious phenomenon culminates in death of cardiac cells that were viable immediately before myocardial reperfusion. 1 New strategies that directly target the reperfusion phase could improve clinical outcomes of acute myocardial infarction. [2][3][4] One such strategy, first described by Zhao and colleagues, 5 is called postconditioning. Applying intermittent episodes of myocardial ischemia/reperfusion at the early moments of reperfusion reduces myocardial infarction in every animal species tested, including mice. 6 Similar beneficial effects were recently demonstrated in patients who underwent primary percutaneous coronary intervention for acute coronary occlusion. 3,4 Conclusions-This Editorial see p 1315 Clinical Perspective on p 1336There appears to be a consensus that the delay after which the first reocclusion is established can only be short, but the available data are surprisingly sparse. 7 In a rat model, the beneficial effect of postconditioning was reported as lost when the delay between reperfusion and the first reocclusion was shifted from 10 to 60 seconds. 8 Since then, postconditioning maneuvers were initiated within 1 ...

Although colchicine, a natural product, is one of the oldest drugs still currently available, its possible functions seem to be surprisingly not well-known. Beyond its present medicinal use (gout, familial Mediterranean fever, Behcet's disease, chondrocalcinosis and other crystal arthritis), numerous other conditions have been recently proposed for the use of this drug, including pericardial diseases. However, colchicine appears as a double-edged sword, with underestimated toxicity and frequent side effects. In this review, we present the main pharmacologic features of this drug, with an emphasis on toxicity and highlight its possible applications in the cardiovascular field.