الفهرس 
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Abstract
the e f f e c t s of some ant i-malarial drugs (chloroquine-primaquine)have been examined f o r t h e i r analgesic (pain i n h i b i t i n g ) a c t i v i t i e s the prostaglandins level has been considered t o be the marker f o r such e f f e c t s , since it has been reported t h a t prostaglandins is one of the major mediators f o r pain(8) production (Willis et a l . , 1969). The intravenous administration of chloroquine i n rabbit was able t o reduce s i g n i f i c a n t l y (P < 0.05) the t o t a l prostaglandins l e v e l i n b r a i n t i s s u e . The reduction reached about 250.6 -+ 5.99 nanogram /0.4 gm wet b r a i n t i s s u e (N. = 306.5 +- 4.33) a t a dose of 50 mg/kg.b.wt. On t h e other hand, t h e o r a l administration of primaquine at a dose of 0.75 mg/kg.b. wt . produced a non s i g n i f i c a n t decrease (P > 0.05) i n the basal prostaglandins l e v e l of the t o t a l brain content. The l a t t e r could be explaned v i a d i f f e r e n t p o s s i b i l i t i e s , F i r s t l y ; the administered dose was not enough to produce a s i g n i f i c a n t reduction of prostaglandins, Secondly; the drug absorption and pharmacokinetic properties didn’t allow enough concentration t o reach the brain t i s s u e s , Thirdly; the pharmacodynamic p r o p e r t i e s o r the drug i t s e l f has no analgesic property. The f i r s t step in the biosynthesis of both prostanoids and leukotrienes is the r e l e a s e of f r e e arachidonic acid from membrane-bound phospholipids. The enzyme which responsible f o r t,his release is phospholipase A2. I n h i b i t i o n of the phospholipase step i n the arachidonic acid cascade e f f e c t i v e l y ”turn offH the formation of a l l cyclooxygenase and lipoxygenase metabolites by s t a r v i n g these enzymes of t h e i r precursors. Quinacrine dihydrochloride (Mepacrine) the first drugs to be used experimentally was the antimalarial agent, It is highly effective i n antagonizing and i n h i b i t i n g the phospholipase A2 enzyme (Peers and Hoult ,1986) thus leading t o marked reduction i n the prostaglandins l e v e l .