Couldn't generate code for the following reason:
Variable has units dimensionless which are incompatible with the units micromolar on a connected variable.; 
  In MathML apply element.
  In MathML math element.
  In CellMLComponent element with cmeta:id O with name O.
  In Model element with cmeta:id lebeau_model_1999_version02 with name lebeau_yule_groblewski_sneyd_1999_version01.