Objective To observe the effect of chronic stress stimulation on aging and the effect of acupoint catgut-embedding therapy on structural changes of hippocampal pyramidal neurons in senile chronic stress rats

so as to reveal its mechanisms underlying resisting senility.Methods Forty-eight male SD rats were randomly divided into normal control

senility model

senility+stress and senility+stress+catgut-embedding(catgut-embedding)groups(n=12in each group).Senility model was established by intraperitoneal injection of D-galactose liquor

once daily for 8weeks;and chronic stress was produced by restricting the rat in an inmovable cylinder for 1-4hprogressively

once daily for 4weeks.Catgut embedment(0.4-0.6cm in length)was applied to"Baihui"(GV 20)and"Shenshu"(BL 23)

"Neiguan"(PC 6)and"Ganshu"(BL 18)alternatively by using a surgical needle

once a week

8weeks altogether.The brain tissue containing hippocampus was cut into sections to be stained with H.E.technique

and the number of the hippocampal pyramidal neurons of CA 3region was counted under optical microscope.The ultrastructure of pyramidal neurons in the left CA 3region of the hippocampus was observed by electron microscope(2rats for each group).Results Compared with the normal control group

the numbers of hippocampal pyramidal neurons in the senility model group and senility+stress group were remarkably decreased(P<0.05

P<0.01).The number of pyramidal neurons was obviously fewer in the senility+stress group than in the senility model group(P<0.01).In comparison with the senility+stress group

the number of pyramidal neurons in the catgut-embedding group was considerably increased(P<0.01).Results of optical microscope showed that the pyramidal cells were sparse in the senility model and very sparse in the senility+stress group

and relatively richer in the catgut-embedding group.Findings of the electron microscope displayed that the pyramidal neurons presented an injured state including shrank soma

pyknosis of the cellular nucleus

atrophia of nucleoli

onglobation of intranuclear caryotin

decreased glycogen granules

etc.in the senility model group

and an extremely irregular shape

partial apoptosis

severer pyknosis of the cellular nucleus

more edema blank regions

etc.in the senility+stress group.These situations of pyramidal cells in the hippocampal CA 3region were relatively milder in the catgut-embedding group.Conclusion Chronic stress may aggravate the damage of hippocampal pyramidal neurons in senile rats

which can be improved by catgut-embedding therapy.