Change title fontsize in heatmap.2 function?

I am using the heatmap.2 package to make a heatmap:

heatmap.2(as.matrix(FOOBAR.txt[rowSums (abs(FOOBAR.txt)) != 0,]),
          col=scaleyellowred,
          margins = c(10, 20),
          trace="none",
          xlab = "Comparisons",
          ylab ="gene",
          lhei = c(2, 8),
          scale=c("none"),
          symbreaks=T,
          cexRow=0.5,
          cexCol=.7,
          main="gene comparisons")

The output gives me a heatmap look like I want and looks good with the exception that the main title font is large. How do I decrease the font size of the title? I can't seem to figure it out. I can alter the font of the axis labels but not the title.