Enkephalin and dynorphin neuropeptides are differently correlated with locomotor hypersensitivity and levodopa-induced dyskinesia in parkinsonian rats.

In this study, we measured PPENK, PDYN, D1R and D2R mRNA levels by in situ hybridization in the striatum of 6-OHDA hemi-parkinsonian rats treated with l-DOPA (PD+l-DOPA group), along with two control groups (PD+saline and naive+l-DOPA). We found different levels of expression of PPENK, PDYN, D1R and D2R mRNA across the experimental groups and correlated the changes in mRNA expression with dyskinesia and locomotor variables assessed by open field test during several phases of l-DOPA treatment. Both PDYN and PPENK mRNA levels were correlated with the severity of dyskinesia, while PPENK mRNA levels were also correlated with the frequency of contralateral rotational movements and with locomotor variables. Moreover, a strong correlation was found between D1R mRNA expression and D2R mRNA expression in the PD+l-DOPA group. These findings suggest that, in parkinsonian animals treated with l-DOPA, high levels of PPENK are a prerequisite for a locomotor sensitization to l-DOPA treatment, while PDYN overexpression is responsible only for the development of dyskinesia. PMID: 27072528 [PubMed - as supplied by publisher]
Source: Experimental Neurology - Category: Neurology Authors: Tags: Exp Neurol Source Type: research