Effects of cyclic nucleotides on the longitudinal internal resistance in the rabbit sinus node

The effect of dibutyryl cyclic AMP as well as dibutyryl cyclic GMP on the longitudinal internal resistance was studied in the rabbit sinus node strips by means of microelectrode and sucrose gap techniques. Dibutyryl cyclic AMP added to the sucrose gap decreased the resistance and increased the spontaneous rate whereas dibutyryl cyclic GMP evoked the opposite effects. These results suggest that cyclic nucleotides influence the cell coupling in the sinus node.