Myotonia and Chloride-Reply

In Reply.—  I have belatedly reviewed Dr Bretag's article and find that we essentially agree in our independent assessments of the theoretical relationship between reduced chloride conductance of the sarcolemma and the repetitive action potentials observed in myotonia.I cannot agree, however, with several of Dr Bretag's comments. As was indicated in my article, the initial sequence of simulations presented therein did not include terms for contributions from the T-tubular system. The computational complexity required to accurately include these terms would have restricted the flexibility of the model in these initial studies requiring multiple simulations. Dr Bretag refers to the pronounced effects on simulated myotonia that he observes from inclusion of a passive resistivecapacitative representation of the T-system. However, it is clear from recent work^1.2 that the T-tubular system is not passive, but rather actively conducts action potentials down its length. Thus, it is incorrect to consider the T-system as a