Fig. 5.

Pressure overload induces an increase in mast cell density in the cardiac plexus. Whole mounts of the cardiac plexus from control and pressure overload-treated animals were fixed and stained for immunohistochemical analysis. Mast cell density was determined with antibody labeling for histamine (rabbit anti-histamine, 1:500 and donkey anti-rabbit-Cy3, 1:500). The number of histamine-immunoreactive cells in a 100-mm² area was determined in five different preparations and the mean ± SD is shown (open bars, control preparations; striped bar, PO preparations). There was a significant (**P < 0.003) increase in mast cell density in the PO tissues.