The
latex of the wild growing plant Calotropis procera produces
inflammation of the skin and mucous membranes upon accidental exposure. On local administration it elicits an intense inflammatory response due to the release of
histamine and
prostaglandins that is associated with
hyperalgesia. In the present study we have evaluated the anti-inflammatory and antinociceptive activity of
oxytocin and
melatonin against rat paw
edema induced by dried
latex (DL) of C
procera and compared it with that against
carrageenan-induced paw
edema. Aqueous extract of DL of C
procera or
carrageenan (1%) was injected into the subplantar surface of the rat paw and the paw volume was measured at 0, 1, 2, 3, 4, 6, 10, and 24 hours. The associated hyperalgesic response and functional impairment were also evaluated concomitantly by dorsal flexion
pain test, motility test, and stair climbing ability test. The inhibitory effect of
oxytocin and
melatonin on
edema formation and hyperalgesic response was compared with
dexamethasone. DL-induced
edema formation was maximum at 2 hours and was associated with decreased pain threshold and functional impairment. Treatment with
melatonin significantly attenuated the edematous response while both
oxytocin and
melatonin increased the pain threshold and improved functional parameters. Both
oxytocin and
melatonin significantly inhibited the
hyperalgesia associated with DL-induced paw
edema.
Oxytocin was found to be as effective as
melatonin in ameliorating the hyperalgesic response. However, it was found to be less effective than
melatonin in attenuating
edema formation.