Figure 5
A. The effects of diphenhydramine on the response of gland cell epithelium to histamine. The responses to histamine, like those to ACh, are transient. However, the response to histamine decays more rapidly than that for ACh. Note that diphenhydramine causes increasing inhibition with increasing concentration of inhibitor (A and inset A.1) without a decrease in maximum response of the histamine action. The range of concentrations at which inhibition occurs is similar to those that inhibited the ACh response (n = 9). Inset A.2 shows the Schild plot generated from diphenhydramine data. Note that when the slope of the line (red) shown in the inset was set to1, the calculated pA2 is 6.5 ± 0.2. However the least squares fit to these data had a slope of 1.6 (blue line) with estimated X intercept of -10.8 ± 2.4, suggesting that the underlying assumptions of the Schild analysis were not met. B. The effects of fexofenadine on gland cell responses to histamine. ΔIsc in response to histamine are blocked by fexofenadine. Fexofenadine decreased the maximum ΔIsc and caused a small shift to the right. Inset B shows the concentration response relationships derived from these data (n = 8).