Relaxation phase calcium

It has been postulated that 2-PAM exerts its cardiac action in rabbit atria through its alteration of calcium metabolism. The relaxation phase of skeletal muscle contraction seems to be directly affected by the sarcoplasmic reticulum because of its ability to sequester calcium actively.29,46 a similar role has been suggested for the sarcoplasmic reticulum in cardiac muscle. 6,83 The onset of muscle contraction takes place when calcium reaches a crit-cal concentration. This contraction is later reduced by the increased calcium-sequestering activity of the sarcoplasmic reticulum. Thus, 2-PAM can affect this process by decreasing the rate of calcium uptake by the sarcoplasmic reticulum, which results in increasing the time required to reduce the calcium concentration enough to allow relaxation to take place. This was demonstrated by the Increase in the relaxation phase. It was suggested that this... 

I call magnesium the relaxer because it stimulates the relaxation phase in muscle tissue, including the heart muscle, just as calcium stimulates the contraction phase. Many people are familiar with milk of magnesia, an antacid suspension of magnesium hydroxide sometimes used as a cathartic, and with Epsom salts, a bath salt of magnesium sulfate that produces wonderful relaxation. Dr. C. Norman Shealy considers magnesium a crucial neurochemical, which I will discuss in the next few pages. 

Verapamil. Verapamil hydrochloride (see Table 1) is a synthetic papaverine [58-74-2] C2qH2 N04, derivative that was originally studied as a smooth muscle relaxant. It was later found to have properties of a new class of dmgs that inhibited transmembrane calcium movements. It is a (+),(—) racemic mixture. The (+)-isomer has local anesthetic properties and may exert effects on the fast sodium channel and slow phase 0 depolarization of the action potential. The (—)-isomer affects the slow calcium channel. Verapamil is an effective antiarrhythmic agent for supraventricular AV nodal reentrant arrhythmias (V1-2) and for controlling the ventricular response to atrial fibrillation (1,2,71—73). 

---