ABSTRACT
Long-term potentiation (LTP) of synaptic transmission between the dendrites of the pyramidal cells of CA[ region and the Schaffer-commissu-ral pathway was induced with electric stimulation in the isolated hippocampal slices of rats.The effects of 3 convulsants,soman,kianic acid.and picroto-xin,on the induction of LTP in this region were observed.It was found that a short series of electric impulses could effectively induce LTP in most of the slices of the hippocampus and the amplitude of the population spikes showed a similar change as the field excitatory postsynaptic potential did in the rising phase.Picrotoxin could facilitate the induction of LTP when it evoked an epileptoform electric activity in the slices,kianic acid could also evoke an epileptoform activity but significantly blocked the induction of LTP,and soman could not evoke obvious epileptoform activity but blocked the induction of LTP.The above findings suggest that a short series of electric impulses can effectively induce LTP between the pyramidal cells and the Schaffer-commisural pathway in the CA1 region,the effects of epileptoform activity on the induction of LTP depends on the mechanism to evoke the epileptoform activity,and the effects of soman on the induction of field potential may involve the noncholi-nergic system in the synaptic connections.
ABSTRACT
The actions of the hippocampal formation were studied by recording the electrical activities of a single neuron of that area. Two different reactions of some neurons in CAl, CA2 and the dentate gyrus might occur after peripheral noxious stimulations, that is, the increasing of the reaction frequency of the nociceptive excited neurons(NEN) and the decreasing of the reaction frequency of the nociceptive inhibited neurons (NIN). Electrical acupuncture of the "points" would result in inhibiting effect on most of the NENs but disinhibiting effect on NINs, Identical effect to that of acupuncture could be created by injecting morphine to the experimental animals. Electrical stimulation of the nucleus raphe magnus or para-aqueduct gray matter(PAG) could affect the NENs and NINs in the hippocampus, and the results were similar to that of acupuncture. When 5-HT was injected into the lateral ventricle or applied to the 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 electrical activities of the neurons of the hippocampal formation might be related to the activities of the endogenous 5-HTergic neurons, or to the endogenous morphine-like substance. The NENs would be inhibited after large amounts of GABA were injected into the lateral ventricle. The inter-relationship between this phenomenon and the activities of GABAergic interneu.rons in the hippocampus awaits further investigation.
ABSTRACT
This paper is to introduce our newly designed driving system used to push a microelectrode forward into the recording position in animal experiments. The instrument consists of two parts: 1. the hydraulic fine manipulator and 2. the holding mechanism and the secrew driving device of the microelectrode.Carefully pass a long glass shaft microelectrode through a stainless steel guide tube. Both the microelectrode and the guide tube are fixed on the frame of the instrument with two holding mechanisms. The frame is then connected to the chassis of the instrument which has previously been embedded in the skull of the experimental animal. Turn the screw driving device and both the microelectrode and the guide tube are moved forward. Stop turning when the guide tube penetrates the dura. Then the hydraulic fine manipulator is used to push the microelectrode into the recording position.A long glassshaft microelectode produces little injury to the brain tissue, thus it facilitates the repeated experiments on animals. The chassis of the driving system is implanted into the skull of the experimental animal with stereoscopic technique and its relative position with the brain tissue can not be changed during experiment. Slight movement of the animal head will in no way interfere with the recording.