title: Photobiomodulation preserves behaviour and midbrain dopaminergic cells from MPTP toxicity: evidence from two mouse strains.
abstract: BACKGROUND
  We have shown previously that near-infrared light (NIr) treatment or photobiomodulation neuroprotects dopaminergic cells in substantia nigra pars compacta (SNc) from degeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in Balb/c albino mice, a well-known model for Parkinson's disease. The present study explores whether NIr treatment offers neuroprotection to these cells in C57BL/6 pigmented mice. In addition, we examine whether NIr influences behavioural activity in both strains after MPTP treatment. We tested for various locomotive parameters in an open-field test, namely velocity, high mobility and immobility.
  
  
  RESULTS
  Balb/c (albino) and C57BL/6 (pigmented) mice received injections of MPTP (total of 50 mg/kg) or saline and NIr treatments (or not) over 48 hours. After each injection and/or NIr treatment, the locomotor activity of the mice was tested. After six days survival, brains were processed for TH (tyrosine hydroxylase) immunochemistry and the number of TH⁺ cells in the substantia nigra pars compacta (SNc) was estimated using stereology. Results showed higher numbers of TH⁺ cells in the MPTP-NIr groups of both strains, compared to the MPTP groups, with the protection greater in the Balb/c mice (30% vs 20%). The behavioural tests revealed strain differences also. For Balb/c mice, the MPTP-NIr group showed greater preservation of locomotor activity than the MPTP group. Behavioural preservation was less evident in the C57BL/6 strain however, with little effect of NIr being recorded in the MPTP-treated cases of this strain. Finally, there were differences between the two strains in terms of NIr penetration across the skin and fur. Our measurements indicated that NIr penetration was considerably less in the pigmented C57BL/6, compared to the albino Balb/c mice.
  
  
  CONCLUSIONS
  In summary, our results revealed the neuroprotective benefits of NIr treatment after parkinsonian insult at both cellular and behavioural levels and suggest that Balb/c strain, due to greater penetration of NIr through skin and fur, provides a clearer model of protection than the C57BL/6 strain.
authors.affiliation: CEA, LETI, CLINATEC, Grenoble 38054, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Moro
authors.forename: Napoleon
authors.initials: N
authors.lastname: Torres
authors.forename: Nabil
authors.initials: N
authors.lastname: El Massri
authors.forename: David
authors.initials: D
authors.lastname: Ratel
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Johnstone
authors.forename: Jonathan
authors.initials: J
authors.lastname: Stone
authors.forename: John
authors.initials: J
authors.lastname: Mitrofanis
authors.forename: Alim-Louis
authors.initials: AL
authors.lastname: Benabid
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D059290:Dopaminergic Neurons / Q000473:pathology / Q000528:radiation effects*; D005106:Exploratory Behavior / Q000528:radiation effects; D007259:Infrared Rays; D028022:Low-Level Light Therapy; D020267:MPTP Poisoning / Q000473:pathology* / Q000628:therapy*; D008297:Male; D008636:Mesencephalon / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000528:radiation effects; D009498:Neurotoxins / Q000633:toxicity; D013045:Species Specificity; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D009498:Neurotoxins; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D014446:Tyrosine 3-Monooxygenase