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Purpose Blood pressure is an important vital signs of the life.Some disease caused by the abnormal regulation of blood pressure especially hypertension,its incidence rate is very high.Some kinds of abnormal blood pressure always occurred during the night.Regulation of blood pressure during sleep is still mysteriously.Some evidence has shown that hippocampus has an important role in the regulation of blood pressure during sleep.But some contradiction is always existed.The purpose of this project that would like to further explore the specific regulatory mechanisms of the hippocampal network in the state of sleep.Methods About 30 urethane-anesthetized rats was adopted as a simple sleep model in this project.Hippocampal network electrical activity and femoral artery blood pressure with EKG are all recorded simultaneously.And all the data will be analyzed offline to explore the cellular mechanism of cardiovascular regulation in sleep state.Results: 1)Cyclic alternation pattern of hippocampal field potential has been observed.This pattern mainly contains two kinds of oscillation inclues theta oscillation and slow oscillation(n=24,24/30=80%).This characteristic is very similar to the electroencephalogram in sleep.Blood pressure and heart rate are also cyclically changed in a narrow band at the same time.The femoral artery blood pressure in the theta phase was lower than in the slow oscillation phase,the value is about 13.64±3.31mmHg.But the heart rate in the theta phase was higher than in the slow oscillation phase,the value is about 5.14±0.9 bpm.2)Two kinds of theta related cells in the hippocampal network has been recorded.Theta-on cell unit discharge was increased when theta oscillation occurred,(n=15).At the same time,the heart rate was also increased.When the slow oscillation and spindle occurred,the unit discharge and heart rate were also decreased.Spindle wave length is proportional to interspike interval of theta-on cell unit discharge (r=0.902,p<0.05).And theta-on cell unit discharge was phase-locking to the positive phase of slow oscillation; The theta-off cell unit discharge was decreased or stopped when theta oscillation occurred(n=9).At the same time,the heart rate was increased.When the slow oscillation and spindle occurred,the theta-off cell unit discharge increased and heart rate decreased.And theta-off cell unit discharge was phase-locking to the negative phase of slow oscillation.Conclusions: 1.Urethane-anesthetized rats is a simple sleep model.And it has the characteristic of cyclical cardiovascular alternation events during sleep.2.Slow oscillation originated from cortex has a strong modulation to theta-related cells in hippocampus,and spindle oscillation originated from thalamus has a selective inhibition on the theta-on cell in hippocampus.Interactions between theta related cells in hippocampal network and some key structure such as cortex、thalamus、brain stem are all involved in the regulation of sleep cardiovascular regulation.3.Hippocampal theta oscillation is correlated with the acceleration of heart beat in sleep cycle.But cortex slow oscillation and thalamus spindle oscillation maybe is correlated with deceleration of heart beat.