Agonist concentration gradients as a generalizable regulatory implementation strategy.

This article proposes a general mechanism by which biphasic dose-response relationships occur in pharmacological and toxicological experimental systems. Such biphasic responses are mediated via a strategy of differential binding to stimulatory and inhibitory receptor subtypes based on agonist concentrations. Such a strategy is widely seen in pharmacological systems and has been demonstrated in toxicological-related biphasic dose responses in which the treatment altered levels of endogenous agonists.