Key result
Myogenic activity could be initiated in a deganglionated Limulus heart by immersion in isotonic sodium chloride or by inflation with air, both of which were resistant to tetrodotoxin and procaine.
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Demonstrates that myogenic activity can be induced in the neurogenic heart of Limulus polyphemus via specific ionic or mechanical stimuli, independent of sodium channels blocked by tetrodotoxin.
Myogenic activity could be initiated in a deganglionated Limulus heart in two different ways. If immersed in "isotonic" sodium chloride (600 mM) the heart began to contract locally in 5-10 minutes. These contractions were seldom coordinated and were due to overshooting spikes of long duration (100 msec.). Spike height was a function of the external sodium ion concentration. The activity was completely abolished upon addition of 2-3 mM CaCl2. A second type of myogenic activity could be initiated by inflating a deganglionated heart with air and immersing it in sea water or physiological solution. The contractions began in 10-20 min in one of the anterior segments and travelled peristaltically in both directions. Activity was caused by non-overshooting spikes. Both types of myogenic activity were resistant to tetrodotoxin (TTX, 10-5 M) and procaine (10-4 M).
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Fred Lang (1971) studied Deganglionated Limulus heart. Isotonic sodium chloride or inflation with air was evaluated on Myogenic activity (contractions and spikes). Myogenic activity could be initiated in a deganglionated Limulus heart by immersion in isotonic sodium chloride or by inflation with air, both of which were resistant to tetrodotoxin and procaine.
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