Dopamine (DA) and SKF81297 stimulate an increase in matrix metalloproteinase (MMP) activity. DA and SKF81297 stimulate increased cleavage of β-dystroglycan in striatal slices (a and b). Densitometric data shown in (a) are from four vehicle and five DA-treated slice lysates, and the difference is significant (two-tailed t-test, t7 = 3.259, *P = 0.0139). Densitometric data shown in (b) are from three vehicle and four SKF81297-treated slice lysates, and the difference is significant (two-tailed t-test, t5 = 4.22, *P = 0.0083). DA (60 min) also simulates increased β-dystroglycan cleavage in cultured astrocytes (c). Densitometric results represent the average fold increase from four vehicle and four DA-treated astrocyte culture lysates. The difference between β-DG30 in vehicle and DA-treated lysates was significant (two-tailed t-test, t6 = 2.87, *P = 0.0284). GAPDH is shown as a loading control.