Objective        To determine the effect of D

1

-like dopamine receptor on neuropeptide Y (NPY)-mediated proliferation in primary cultured vascular smooth muscle cells （VSMCs） derived from thoracic aorta of Sprague-Dawley(SD) rats.        Methods        After VSMCs were isolated from SD rat thoracic aorta and identified by morphology and immunocytocchemistry

the cells at passage 4 to 8 were treated by 10

-8

t

o 10

-11

mol/L NPY in presence or absence of D

1

-like receptor agonist fenoldopam (10

-8

mol/L)

blocker BIBP3226（10

-6

mol/L）

or antagonist SCH23390 （10

-8

mol/L）to observe NPY-mediated proliferation in VSMCs. The proliferation of VSMCs was investigated by [

3

H

]

-TdR incorporation and MTT assay.       Results        NPY resulted in an increased proliferation of VSMCs in a concentration-dependent manner

with a maximal proliferative amplitude of (77±9)% (P0.05). D

1

-like receptor agonist

fenoldopam

completely blocked the NPY Y

1

-mediated proliferation in VSMCs

although the agonist had no effect on the proliferation of VSMCs by itself

which might be through protein kinase A pathway.       Conclusion        Activation of D

1

-like receptor inhibits NPY Y

1

-mediated proliferation in VSMCs，which might be involved in the pathogenesis of cardiovascular diseases.