Experimental procedure. Twenty-four hours before the experiment,
ratswere anesthetizedwith a solution (0.1 ml) of ketamine (20 mg/ml)
and xylazine (0.64 mg/ml) administered ip. Hair on the dorsal surface
was removed from these animals with electric clippers (Oster Corp.,
Model A2, Milwaukee,WI, USA) using a size 40 blade. The clipped area
was washed with distilled water to remove extraneous matter.