Alterations of Nigral Dopamine Levels in Parkinson’s Disease after Environmental Enrichment and PACAP Treatment in Aging Rats

The neuroprotective effects of environmental enrichment and PACAP (pituitary adenylate cyclase-activating polypeptide) are well-described in Parkinson’s disease. The aim of our study is to investigate the beneficial effects of these factors in aging parkinsonian rats. Newborn Wistar rats were divided into standard and enriched groups according to their environmental conditions. Standard animals were raised under regular conditions. During the first five postnatal weeks, enriched pups were placed in larger cages with different objects. Aging animals received (1) saline, (2) 6-hydroxidopamine (6-OHDA), or (3) 6-OHDA + PACAP injections into the left substantia nigra (s.n.). On the seventh postoperative day, the left and right s.n. were collected. The s.n. of young and aging unoperated animals were also examined in our experiment. We determined the dopamine (DA) levels by the HPLC-MS technique, while the sandwich ELISA method was used to measure the Parkinson disease protein 7 (PARK7) protein levels. In healthy animals, we found an age-related decrease of DA levels. In aging parkinsonian-enriched rats, the operation did not result in a significant DA loss. PACAP treatment could prevent the DA loss in both the standard and enriched groups. All injured PACAP-treated rats showed remarkably higher protective PARK7 levels. The protective effect of PACAP correlated with the increase of the DA and PARK7 levels.