calculated blood vessel dilation force reduction measurement logarithm of the concentration of acetylcholine at which the reduction in force during dilation of a blood vessel is half the maximum value (Log EC50) 2012-03-14T04:24:16Z A calculated value for logarithm of the concentration of acetylcholine (ACh), the ester of acetic acid and choline with chemical formula CH3C=OO(CH2)2-N(+)-(CH3)3 and IUPAC name 2-acetoxy-N,N,N-trimethylethanaminium, which acts as a neurotransmitter, at which the energy exerted during the active expansion in the diameter of a blood vessel in response to the application of ACh is halfway between the highest value, that is the force at greatest constriction (often measured in a pre-constricted blood vessel), and the lowest achievable value of such contractile energy during ACh-induced relaxation of the vessel wall (i.e. the maximum effect of Ach which is the minimum contractile energy). The logarithm of the concentration is the exponent indicating the power to which 10 must be raised to obtain that concentration value. JSmith acetylcholine Log half maximal effective concentration (Log EC50) acetylcholine response/sensitivity measurement