Morphine attenuates neurotoxic effects of MPTP in zebrafish embryos by regulating oxidant/antioxidant balance and acetylcholinesterase activity.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases due to the loss of dopaminergic neurons in the midbrain in the substantia nigra. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxic agent causing disruptions in mitochondria of dopaminergic neurons leading to impaired oxidant-antioxidant balance. Both zebrafish and zebrafish embryos are sensitive to MPTP. In zebrafish embryos, MPTP decreases the dopaminergic cells in the diencephalon by damaging dopaminergic neurons. Morphine is an opioid pain killer and a strong analgesic that is used to treat chronic pain. Until today morphine has been shown to regulate the survival or death of neurons and both protective and destructive effects of morphine have been reported in the central nervous system. This study aimed to evaluate the effects of morphine in MPTP-exposed zebrafish embryos. Developmental parameters were monitored and documented daily during embryonic development. Locomotor activity of zebrafish embryos at 96 h postfertilization (hpf) was determined. Acetylcholinesterase (AChE) activity and oxidant-antioxidant parameters were analyzed by biochemical methods. RT-PCR was used to evaluate bdnf , dj1 , lrrk and pink1 expressions. Morphine treatment improved mortality and hatching rates, locomotor activity, AChE, and antioxidant enzyme activities as well as the expressions of bdnf , dj1 , lrrk and pink1 in a dose-dependent manner that were altered by MPTP. Increased lipid peroxidation supports the role of morphine to induce autophagy to prevent PD-related pathologies. Our study provided important data on the possible molecular mechanism of the therapeutic effects of morphine in PD.