sentence: The therapeutic benefit of GDNF and NRTN has been demonstrated in phenotypic , toxin-induced [ 6-hydroxydopamine ( 6-OHDA ) and 1-methyl-4-phenyl-1 ,2,3,6 - tetrahydropyridine ( MPTP ) ] rodent and non human primate models of PD ( Bilang-Bleuel et al ., 1997 ; Choi-Lundberg et al ., 1997 ; Mandel et al ., 1999 ; Kirik et al ., 2000 ; Kordower et al ., 2000 ; Eslamboli et al ., 2003 , 2005 ; Kordower et al ., 2006 ; Gasmi et al ., 2007a , b ; Ramaswamy et al ., 2007 ; Herzog et al ., 2008 , 2009 ; Su et al ., 2009 ) .