Estrogen as a natural antioxidant of membrane phospholipids peroxidation can block the damage of dopaminergic neurons in substantia nigra (SN) lesioned by exotic toxicant like 6-hydroxydopamine (6-OHDA) to protect dopaminergic neurons in SN.Until now researching the relationship between estrogen and the system of dopaminergic neurons in SN generally adopt ex vivo and acute animal microdialysis experiments which can not reflect estrogens internal proptection of antioxidative stress to dopaminergic neurons.A lot of substantial evidences strongly implied that P50 sensory gating (P50) and dopaminergic neurotransmitter have affinities,P50 can be recorded in a quite and awake state.In the present P50 sensory gating in SN was studied in normal group (F-INT),Parkinsons disease model group with 6-OHDA lesioned SN (F-PD),ovariectomy + 6-OHDA Parkinsons disease model group (F-OVX-PD) and ovariectomy + estrogen replacement + 6-OHDA Parkinsons disease model group (F-OVX-E2-PD) to determine the change of P50 sensory gating in SN on estrogen against dopaminergic neurons depleted by oxidative stress.