Background and Aim: Introduction: Tetrahydrocannabinolic acid (THCA) and Cannabidiolic acid (CBDA) are two majour decarboxylated cannabinoid found in hydroalcoholic extract of female Cannabis sativa flowers, heating change them to Tetrahydrocannabinol (THC) and Cannabidiol (CBD) respectively, chemicals that are able to activate the endocannabinoid system. This investigation is to find out the effects of the central or intrathecal administration (i.t.) of the plant heated extract on the inflammatory paw edema in rat. Methods: Material and methods: The adult male Wistar rats (250-300 g) initially were subjected to i.t. surgery as 8cm of PE-10 cannula was inserted into the spinal subarachnoid space. Groups (n=7) were included: control, sham (salin+tween+ethanol, i.t.) and plant extract treatment (0.01mg/10µ l, i.t.). 5 min after i.t. administration, before and one hour after 0.05 ml injection of formalin 2/5% in the sub plantar region of hind paw, edema volume were recorded using plethysmometer. Results: Results: Hydroalcoholic extracts of heated flowers could significantly reduce formalin-induced paw edema (p<0.05). Conclusion: Conclusion: Carboxylated cannabinoid such as THC and CBD are probably present in the extract which probably elevate the level of central endocannabinoids, especially Anandamide, may be by inhibition of their reabsorption and degrading enzymes. All these can suppress inflammatory paw edema by inhibition at the level of spinal cord; these assumptions are needed to investigate more.

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