Abstract
Rolipram, a specific inhibitor of the phosphodiesterase IV (PDE IV), has recently been shown to exert neuroprotective effects in an Alzheimer transgenic mouse model and in hypoxic-ischemic damage in the rat brain. It activates the cAMP-dependent protein kinase (PKA)/cAMP regulatory element-binding protein (CREB) signaling pathway and it inhibits inflammation. We tested the neuroprotective effects of the specific PDE IV inhibitor rolipram in C57BL/6 mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We found that rolipram administered at 1.25 mg/kg or 2.5 mg/kg doses significantly attenuated MPTP-induced dopamine depletion in the striatum, and reduced the loss of tyrosine hydroxylase-positive neurons in the substantia nigra. There was a bell-shaped dose effect with greater efficacy at the 1.25 mg/kg dose than 2.5 mg/kg and a higher dose of rolipram, 5 mg/kg, had no protective effect and even increased the mortality of animals when co-administered with MPTP. Rolipram did not interact with MPTP in its absorption into the brain and in its metabolism to 1-methyl-4-phenylpyridinium (MPP(+)). Our data show a neuroprotective effect of the PDE IV specific inhibitor rolipram against dopaminergic neuron degeneration, suggesting that PDE IV inhibitors might be a potential treatment for Parkinson's disease.