Abnormal activation of the RhoA/Rho kinase (ROCK) pathway plays a pivotal role in neuroinflammatory and pro-oxidative responses, axonal retraction, and apoptosis. We observed increased expression of RhoA, ROCK II, and ROCK activity in the brain of aged rats, particularly in the substantia nigra. Increased ROCK activity may enhance major mechanisms responsible for aging-related neurodegeneration, thus representing a major factor in the vulnerability of dopaminergic neurons to damage. We also observed that physical exercise decreased ROCK activation in aged rats. This suggests that decreased ROCK activation plays an important role in the neuroprotective effects of exercise observed in several previous studies. Furthermore, the present results suggest that ROCK inhibitors may constitute an effective neuroprotective strategy against aging-related risk of dopaminergic degeneration and possibly against other aging-related neurodegenerative processes.