TY - JOUR T1 - THE BIOLOGICAL ASSAY OF HISTAMINE AND DIPHENHY-DRAMINE HYDROCHOLRIDE (BENADRYL-HYDROCHLORIDE) JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 90 LP - 97 VL - 92 IS - 1 AU - Graham Chen AU - Charles R. Ensor AU - Isabel G. Clarke Y1 - 1948/01/01 UR - http://jpet.aspetjournals.org/content/92/1/90.abstract N2 - A simple and rapid method of biological assay of histamine and Benadryl·HCl in vitro using isolated guinea pigs' ileum is presented. The linear relationship between dose and effect in terms of probits and log dose is utilized to calculate the unknown concentrations of these substances. The mean concentration of histamine producing 50 per cent of the maximal contraction of an ileum was calculated from data of 27 experiments. The medial antihistamine concentration of Benadryl·HCl was determined in 29 experiments. The heterogeneity of the regression coefficients of dose-response lines for histamine and for Benadryl·HCl was tested by the analysis of co-variance. The differences in regression coefficients were found to be highly significant. Suggestions are given for applying the same principles to other types of biological assays and to study the mechanism involved in drug antagonsim. ER -