Unilateral 6-Hydroxydopamine-Lesioned Rat as Relevant Model to Study the Pain Related to Parkinson’s Disease

Abstract

The present study was conducted to test the use of the hemiparkinsonian rat, obtained by the unilateral injection of 6-hydroxydopamine (6-OHDA) in the substantia nigra pars compacta (SNc), as a suitable model for the study of pain associated to Parkinson’s disease (PD). For this purpose, 14 days after unilateral injection of saline or 6-OHDA, rats were assessed for behavioral function in the cylinder test, and apomorphine-induced circling test. Thereafter, at 21st day after injection, mechanical nociceptive threshold was compared between 6-OHD-lesioned and sham-operated animals using electronic von Frey test. Our results showed that injection of 6-OHDA in the SNc induced alterations of behavioral motor as ascertained by predominant use of the ipsilateral forepaw in cylinder test and by the expression of contralateral turnings after subcutaneous injection of apomorphine. The mechanical nociceptive threshold was significantly decreased in 6-OHDA-lesioned rats compared to that of sham-operated rats (p <0.05). This response was reversed by apomorphine treatment. In conclusion, hemiparkinsonian rat, obtained by the unilateral injection of the 6-OHDA in the SNc, can be used to investigate pain symptoms and central pain processing mechanisms related to PD.