The command h = plot() returns the column vector of lineseries handles which does not have the property ‘YDir’. The axes object has this property. You should be looking to set this property for an axes object instead.
I would suggest using ‘plotyyy’ for doing this. ‘plotyyy’ lets you have 3 y-axes. The plot looks less cluttered and is easier to manipulate.
This is available on File Exchange and following is the link: http://www.mathworks.com/matlabcentral/fileexchange/1017-plotyyy
Once you use the ‘plotyyy’ to create the figure, then you can change the ‘YDir’ property of the specific axes by using ‘set’ function:
ax = plotyyy(x,y1,x,y2,x,y3);
set(ax(3),'YDir','reverse');
