In vitro relaxant and spasmolytic effects of essential oil of Pistacia integerrima Stewart ex Brandis Galls

Pistacia integerrima J.L. Stewart ex Brandis (Family: Anacardiaceae) galls are used in Indian ethnomedicine for its anti-asthmatic, sedative and spasmolytic properties, however, there are no scientific studies demonstrating its spasmolytic activity. The present investigation deals with the evaluation of relaxant and spasmolytic activities of the essential oil isolated from the galls of Pistacia integerrima J.L. Stewart ex Brandis (EOPI).In vitro pharmacological assays were carried out on rabbit jejunum spontaneous contractions, guinea pig ileum. The present investigation studied the relaxation of basal tone of isolated guinea pig ileum by possible involvement of NO, prostaglandins, membrane Na⁺ channels, potassium channel, enteric nervous system, adrenoceptors, Ca²⁺ channels. Additional studies were conducted for comparison of the relaxant effects of EOPI on CaCl2 induced contraction in calcium free tyrode solution, effect on nifedipine insensitive component of ACh-induced contraction and on the contractile machinery to intracellular [Ca²⁺] on isolated guinea pig ileum.EOPI at non-relaxing dose potentiated the isoprenaline induced relaxation of rabbit jejunum. EOPI (50µg/mL) exhibited 28% relaxation of basal tone of 60mMK⁺ induced contraction which is unaltered by preincubation with 0.5mM hexamethonium, 0.5µM Tetrodotoxin, 1µM indomethacin, and 100µML-NG-Nitroarginine Methyl Ester (L-NAME). EOPI inhibited Ca²⁺ induced contraction of isolated guinea pig ileum in Ca²⁺ free medium. EOPI (10µg/ml) potentiated the reversal of a KCl-induced tonic contraction has been observed in Ca²⁺ free medium.The present investigation reinforces the use of Pistacia integerrima Stewart ex Brandis as antispasmodic in folk medicine. Moreover, it is demonstrated the involvement of β- adrenoceptors and calcium channels in this activity, but not the participation of nicotinic receptors, Na⁺ channels, prostaglandins or nitric oxide.