Microcystin-LR, a potent protein phosphatase inhibitor, prolongs the serotonin- and cAMP-induced currents in sensory neurons of Aplysia californica.

Microcystin-LR (MCYST-LR), a hepatotoxin produced by cyanobacteria, inhibited purified protein phosphatases (PrPs) from rabbit skeletal muscle and the enzymes from Aplysia with an IC50 of approximately 10(-10) M. MCYST-LR also prolonged both serotonin- (5-HT) and cyclic adenosine monophosphate-induced inward currents in sensory neurons of Aplysia. These results, which are consistent with inhibition of Aplysia PrPs, indicate that MCYST-LR may be a useful probe to elucidate the function of PrPs in neural tissues.