Thermal alterations in onset and offset rate constants for chlorpheniramine

The onset and offset rate constants for chlorpheniramine were obtained using the longitudinal muscle of guinea pig ileum. Between 21 degrees C and 37 degrees C these values follwed linear Arrhenius plots with activation energies similar to other biological systems. Below 18 degrees C the nature of the antagonism changed prohibiting estimation of the rate constants. It is concluded that at higher temperatures the histamine receptor behaves in a uniform manner, but below 20 degrees C a change in properties occurs.