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Pathway Description
Prazosin Action Pathway
Homo sapiens
Drug Action Pathway
Prazosin is an alpha-blocker that causes a decrease in total peripheral resistance and is used to treat hypertension. This drug is indicated for the treatment of hypertension (high blood pressure). Prazosin can be given alone or given with other blood pressure-lowering drugs, including diuretics or beta-adrenergic blocking agents. Alpha-adrenergic receptors are essential for the regulation of blood pressure in humans. Two types of alpha receptors, alpha 1 and alpha 2, both play a role in regulating blood pressure. Alpha-1 receptors are postsynaptic (located after the nerve junction, or space between a nerve fiber and target tissue). In this case, the target tissue is the vascular smooth muscle. Activation of the alpha-1 receptor activates the Gq signaling cascade, which activates phospholipase C. Phospholipase C converts phosphatidylinositol 4,5-bisphosphate to diacylglycerol and inositol 1,4,5-trisphosphate (IP3). IP3 activates the IP3 receptor on the sarcoplasmic reticulum, leading to calcium influx into the cytosol from the sarcoplasmic reticulum. Calcium binds to calmodulin and activates myosin light chain kinase. Myosin light chain kinase is responsicle for phosphorylating myosin light chain. Phosphorylated myosin light chain binds to actin and causes muscle contraction.
Prazosin inhibits the postsynaptic alpha-1 adrenoceptors. This inhibition blocks the vasoconstricting (narrowing) effect of catecholamines (epinephrine and norepinephrine) on the vessels, leading to peripheral blood vessel dilation.
Common side effects of prazosin include dizziness, headache, drowsiness, lack of energy, weakness, palpitations and nausea.
References
Prazosin Pathway References
Basquez R, Pippin MM: Prazosin
Pubmed: 32310419
Wishart DS, Feunang YD, Guo AC, Lo EJ, Marcu A, Grant JR, Sajed T, Johnson D, Li C, Sayeeda Z, Assempour N, Iynkkaran I, Liu Y, Maciejewski A, Gale N, Wilson A, Chin L, Cummings R, Le D, Pon A, Knox C, Wilson M: DrugBank 5.0: a major update to the DrugBank database for 2018. Nucleic Acids Res. 2018 Jan 4;46(D1):D1074-D1082. doi: 10.1093/nar/gkx1037.
Bai Y, Sanderson MJ: Airway smooth muscle relaxation results from a reduction in the frequency of Ca2+ oscillations induced by a cAMP-mediated inhibition of the IP3 receptor. Respir Res. 2006 Feb 23;7:34. doi: 10.1186/1465-9921-7-34.
Pubmed: 16504084
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