Long-term potentiation (LTP) has received considerable attention as a neurophysiological model for studying the biology of memory. The present experiments examined the susceptibility of LTP in the dentate gyrus to modification by peripheral injections of amphetamine and epinephrine. Both drugs enhanced the development of LTP in a dose-related manner comparable to that seen previously in behavioral studies. Such results suggest that the development of this long-lasting electrophysiological change can be regulated by peripheral catecholamine levels in a manner analogous to that seen in behavioral studies of memory.