<正> The actions of thc hippocampal formation were studied by recording the electrical activi-tics of a single neuron of that area.Two different reactions of some neurons in CA2

CA3 and thedentate gyrus ntight occur after peripheral noxious stimulations

that is

increase of the reaction frc-qtcncy of the nociccptive cxcitcd neurons（NENs）and decrcasc of the macron frequeency of thenociocptive inhibited neurons（NENs）.Flctrical acuptmcture of the“points”would result in inhib-iting cffcet on most of the NENs but disinhibiting cffcct on NENs.Identical effect to that ofacupunctre could be creatcd by injecting morphine to the expcrimental animals.Electricalstimulation of thc nucleus raphc magnus or peri-aqueduct gray mattcr could affcct the NENs andNINs in the hippocampus

and the results were similar to that of acupucture.When 5-HT was in-jccted into thc latcral ventricle or applied to thc hippocampal neurons through micro-iontophoresis

effects similar to that of acupuncture also occurred.These facts imply that the effects of peripheral“point”acupuncture on the eletrical activities of the neurons of the hippocampal formation might be rre-lated to the activities of the cndogenous serotoninergic neurons

or to the cndogenous morphine-likesubstance.The NENs would be inhibitod after large amounts of GABA were injected into the lateralventricle.The relationship between this phcnomenon and the acfivites of GABAergic intenrons inthe hippocampus awaits furthcr investigation .