Antagonism of serotonin-activated adenylate cyclase in the liver fluke Fasciola hepatica by levorphanol and dextrorphan

A highly active serotonin (5-HT)¹ -stimulated adenylate cyclase is present in particles from the liver fluke $\text{Fasciola hepatica}$ [1]. This enzyme is activated through a single class of receptors by indoleamines and LSD derivatives. Several recent reports showed that opiates can interact with adenylate cyclase from various tissues [2–4]. In this report we examine the effects of morphine-like drugs upon adenylate cyclase activity in cell free particles from $\text{F}$. hepatica. We report a non-stereospecific inhibition of both basal and serotonin-stimulated cyclase activity and discuss the possible mechanism of this inhibition.