Analgesic activity of the ethanolic extract of Shorea robusta resin in experimental animals

Aim:

Shorea robusta (Sal), an important traditional Indian medicinal plant used in various ailments and rituals and the indigenous use of the resin of this plant as a medicament for treatment of various inflammatory conditions is well documented in literature. In the present study, ethanolic extract of S. robusta resin (SRE) was evaluated for its analgesic activity by making use of different central and peripheral pain models.

Materials and Methods:

The analgesic activity of SRE was assessed by employing different pain models such as, i) hot plate and tail flick tests for central analgesia, ii) acetic acid- induced writhing (peripheral analgesic model), iii) formalin-induced hind paw licking (both central and peripheral model), iv) carrageenan-induced hyperalgesia (peripheral analgesic model) and v) post-surgical pain (peripheral analgesic model).

Results:

The extract produced significant central and peripheral analgesic effects, as is evident from increase in reaction time in hot plate and tail flick tests, inhibition in writhing counts in acetic acid-induced writhing test, inhibition of licking time in formalin-induced hind paw licking, increased pain threshold in paw withdrawal latency in carrageenan-induced hyperalgesia and increased paw withdrawal threshold in post-surgical pain.

Conclusion:

The results of the present study demonstrate marked antinociceptive effects of SRE.

Anti-inflammatory and antipyretic activities of the ethanolic extract of Shorea robusta Gaertn. f. resin

Shorea robusta Gaertn. f. (Sal) is one of the most important traditional Indian medicinal plants. The resin of the plant has been used in the treatment of inflammation in folklore medicine. In the present study, ethanolic extract (70%) of S. robusta resin (SRE) was investigated for its anti-inflammatory and antipyretic activities. Acute inflammation was produced by carrageenan-induced hind paw edema and sub-acute by cotton pellet-induced granuloma in male Wistar rats. The antipyretic activity of SRE was studied using Brewer's yeast-induced pyrexia in rats. The rats were divided into five groups with five animals in each group. Group I was treated with vehicle i.e. 1% v/v Tween-80 and served as control. Groups II to IV were treated with three different doses of SRE (30, 100 and 300 mg/kg orally). Group V was treated with standard drug etoricoxib (10 mg/kg orally). The anti-inflammatory activity of SRE was assessed by per cent reduction in edema volume of carrageenan-induced hind paw edema and by per cent decrease in granuloma formation in cotton pellet-induced granuloma test. SRE (100 and 300 mg/kg) produced a significant reduction in edema volume and decrease in granulation tissue formation in rats. Significant reduction in pyrexia was observed at all the dose levels of SRE i.e. 30, 100 and 300 mg/kg. The results of the present study demonstrated anti-inflammatory and antipyretic activities of S. robusta resin and supported its traditional therapeutic use in painful inflammatory conditions and fever.

Wound healing activity of ethanolic extract of Shorea robusta Gaertn. f. resin

The ethanolic extract of S. robusta resin (10 and 30 % w/w applied locally in excised and incised wounds) produced a dose-dependent acceleration in wound contraction and increased hydroxyproline content and tensile strength of wounds in rats. The results demonstrate wound healing activity of ethanolic extract of S. robusta resin.

Effect of KATP channel openers on myogenic and neurogenic responses in goat urinary bladder

Isolated goat detrusor muscle exhibited spontaneous contractility with an irregular amplitude and frequency. The spontaneity of detrusor muscle exhibited a mean amplitude as 11.99 +/- 0.83 mm and frequency as 1.37 +/- 0.16/min. KATP-channel openers namely, cromakalim or pinacidil (10(-7) - 10(-4) M) added cumulatively, elicited a concentration-related inhibition of both amplitude and rate of spontaneous contractions. The mean IC50 values for both amplitude and frequency for cromakalim were 3.3 x 10(-6) M and 2.9 x 10(-6) M, respectively; and for pinacidil were 2.0 x 10(-5) M and 1.5 x 10(-5) M, respectively. Glibenclamide, a KATP-channel blocker inhibited the cromakalim-induced concentration-related relaxation of spontaneous contractions with a significant increase in its mean IC50. ACh-induced concentration-related contractile response was inhibited in the presence of either cromakalim (10(-4) M) or pinacidil (10(-4) M). The mean EC50 value of ACh, in the presence of cromakalim (2.5 x 10(-3) M) was significantly increased as compared to the control (1.2 x 10(-6) M). In the presence of glibenclamide (10(-5) M) the inhibitory effect of cromakalim was significantly reduced with consequent decrease in the EC50 value (1.9 x 10(-5) M). Application of EFS (30 V and 5 ms) on goat urinary bladder strips at 1, 2, 5, 10, 20 and 30 Hz elicited frequency-related contractile responses. Both cromakalim and pinacidil caused a rightward shift in the frequency-related contractile response curve with significant increase in the mean EF25 and EF50 values, respectively. In the presence of glibenclamide (10(-4) M), the frequency-related inhibitory response curve was shifted to left with significant (P < 0.001) increase in the mean EF25, EF50 and EF75. The present results suggest that in the goat detrusor muscle, agonist and EFS-induced contractile responses were more potently inhibited by cromakalim than pinacidil with activation of glibenclamide sensitive KATP channels.

Effects of oxidizing and reducing agents on ovine pulmonary artery responses to nitric oxide donors, sodium nitroprusside and 3-morpholino-sydnonimine

Nitrovasodilators-sodium nitroprusside (SNP; 10(-9)-10(-4) M) and 3-morpholino-sydnonimine (SIN-1; 10(-9)-10(-4) M) produced concentration-dependent relaxation of the fourth generation sheep pulmonary artery, preconstricted with 5-hydroxytryptamine (1 microM). Oxidizing agents [oxidized glutathione (GSSG, 1 mM) and CuSO4 (5 and 20 microM)] and reducing agents [dithiothreitol (DTT, 0.1 mM), ascorbic acid (1 mM) and reduced glutathione (GSH, 1 mM)] caused opposite effects on nitric oxide (NO)-induced vasodilation in the artery. Ascorbic acid and GSH potentiated the NO responses, while GSSG and CuSO4 inhibited relaxation caused by the nitrovasodilators. DTT, however, reduced the relaxant potency and efficacy of SNP and SIN-1. Pretreatment of the pulmonary artery strips with DTT (0.1 mM) inhibited SNP (10 microM)-induced Na(+)-K(+)-ATPase activity, while ascorbic acid (1 mM) and GSH (1 mM) had no effect either on basal or SNP (10 microM)-stimulated 86Rb uptake, an index of Na(+)-K(+)-ATPase activity, in ovine pulmonary artery. The results suggest that reducing agents like ascorbic acid may have beneficial effect in improving the vascular function under oxidative stress.