Histamine-
induced paw edema occur in earlier stage in mounting of vas-
cular reaction in the chemically induced inflammation. Here,
swelling occurs primarily due to action of histamine. Gen-
erally, histamine is released following the mast cell degran-
ulation by a number of inflammatory mediators including
interleukin-1 (IL-1). This is likely to evoke the release of
neuropeptides as well as release of prostaglandins and mono-
hydroxy eicosatetraenoic acid from endothelial cell leading
to hyperalgesia and other proinflammatory e
ff
ects [
96
].
Procedure
:Theprocedureissameasthatofcarrageenan-
induced paw edema, only instead of carrageenan the rats
are challenged by a subcutaneous injection of 0.1 mL of 1%
solution of histamine into the subplantar side of the left
hind paw. The paw volume is measured and the percent
inhibition of inflammation is calculated and compared with
control group with the formula: