Abstract
The influence of intracellular injection of cAMP on the electrical coupling of canine Purkinje cells was investigated. It was found that the nucleotide enhanced reversibly the cell-to-cell communication through an increase in junctional conductance. Dibutyryl cAMP (5·10 −4 M) plus theophylline (0.4 mM) decreased appreciably the intracellular longitudinal resistance ( r i). The interactions of cAMP and Ca on the electrical coupling were also investigated. The nucleotide and Ca have opposite effects on the electrical coupling. In the presence of high [Ca 2+] o solutions (6 mM), the intracellular injection of cAMP causes a transient increase in the coupling coefficient followed by an appreciable decrease in cell-to-cell coupling. This reduction in intercellular communication was reversed by injecting EGTA into the same cell. The results of this study support the view that cAMP is a modulator of junctional conductance in cardiac muscle and that the compound interacts with Ca in the control of intracellular communication.
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