tcsc2000 Scopolamine (hydrobromide)

Scopolamine hydrobromide is a high affinity (nM) muscarinic antagonist. 5-HT₃ receptor-responses are reversibly inhibited by Scopolamine with an IC₅₀ of 2.09 μM.

IC50 & Target: IC50: 2.09 μM (5-HT₃ receptor)^[1]


mAChR^[1]

In Vitro: Application of Scopolamine to oocytes expressing 5-HT₃ receptors does not elicit a response when applied alone, but causes a concentration-dependent inhibition of the response during a co-application of 2 μM 5-HT. The pIC₅₀ value for Scopolamine is 5.68±0.05 (IC₅₀=2.09 μM, n=6) with a Hill Slope of 1.06 ± 0.05. This gave a K_b of 3.23 μM. The same concentration-dependent effect is also seen when Scopolamine is applied during the 5-HT application. To further test for a competitive binding at the 5-HT₃ receptor, the competition of unlabelled Scopolamine is measured with [³H]granisetron, an established high-affinity competitive antagonist at these receptors. Scopolamine displays concentration-dependent competition with 0.6 nM [³H]granisetron (~K_d), yielding an average pK_i of 5.17±0.24 (K_i=6.76 μM, n=3)^[1].

In Vivo: In the histopathology study, there is no significant change in the histology of the brain. However, it is observed that there is a reduction in density of cells in the hippocampus of the control mice pretreated with Scopolamine who received only distilled water^[2]. Scopolamine administration alone significantly increases the activity of Acetylcholinesterase enzyme (AchE) (7.98±0.065; P<0.001) when compared to the normal group (3.06±0.296). The animals treated with Scopolamine report a significant increase (34.61±4.85; P<0.01) in levels of malondialdehyde (MDA) as compared to the normal group (12.82±2.86). The Scopolamine-treated group shows significant decrease in reduced glutathione (GSH) level (P<0.001; 0.1504±0.03) as compared to the normal group (0.3906±0.02). The Scopolamine-treated rats show a significant increase in the concentration ofβ amyloid (Aβ_1-42) (P<0.001; 146.2±1.74) as compared to the normal group (43.21±3.46)^[3].