5-hydroxytryptamine (serotonin): Biphasic dose responses

This article briefly summarizes the occurrence of biphasic dose-response re lationships associated with 5-hydroxytryptamine (5-HT) receptor systems, as well as 5-HT agonists and antagonists. Such biphasic responses have been r eliably reported in multiple experimental settings that explored a broad ra nge of responses, including aggressive behavior, cardiovascular functioning , muscle relaxation, and interactions with other receptor systems such as a drenergic interaction as well as with neurotransmitters such as NMDA.