Objective      To determine the effect of N

ω

-nitro-L-arginine methyl ester (L-NAME) on the spatial learning and memory abilities and the capillaries in CA1 region of rat hippocampus.       Methods      After the catheter was successfully inserted into lateral ventricle

in the L-NAME group

1 μmol/μL L-NAME was injected into the lateral ventricle of each rat at a dose of 5 μL once a day for 28 d

and in the sham group

the same dose of saline was injected into the lateral ventricle. Then

Morris water maze t

est was used to test the spatial learning and memory abilities. After the Morris water maze test

the NOS activity and NO content in the hippocampal tissues were measured. The total volume of hippocampus and hippocampus CA1 region

and the total length

total volume and total surface area of the capillaries in CA1 region were determined using stereological techniques.       Results      The water maze results showed that the time latency of the sham group was significantly shorter than that of the L-NAME group (P=0.006). Both NOS activity and NO content in the hippocampus of the L-NAME group were significantly lower than those of the sham group (P0.01). The total volume of the hippocampus and CA1 region had no significant difference between the L-NAME group and the sham group (P0.05). The total length

total surface area and total volume of the capillaries in the CA1 region of the L-NAME group were significantly less than those of the sham group (P0.05).       Conclusion      L-NAME induces significant decline in the spatial learning and memory abilities of the rats and significant decrease in the total length

total surface area and total volume of the capillaries in the CA1 region of rat hippocampus.