tailieunhanh - Parkinson disease and related disorders part - part 4

ầm quan trọng của đầu vào cholinergic trong các quy định của tế bào thần kinh GPE vẫn còn được khám phá. . Neuropeptide afferents GPE của . Enkephalin GPE đặc trưng bởi sự hiện diện của immunoreactivity dày đặc để enkephalin. Mức enkephalin trong GPE chỉ là lần thứ hai của thể vân | NEUROCHEMISTRY OF PARKINSON S DISEASE 177 Serotonin Serotonergic innervation to GPe is less intense than GPi Lavoie and Parent 1990 and 5-HT levels are lower in GPe in MPTP models of PD Pifl et al. 1991 . . Acetylcholine The GPe receives a small cholinergic input from PPN Garcia-Rill 1991 . The significance of cholinergic input in the regulation of GPe neurons remains to be explored. . Neuropeptide of GPe afferents . Enkephalin The GPe is characterized by the presence of dense immunoreactivity to enkephalin. The level of enkephalin in GPe is second only to that of striatum. Enkephalin immunoreactivity is derived from the striatopallidal projection of the indirect pathway as well as neurons that are intrinsic to GPe that also express GABA and enkephalin Hoover and Marshall 1999 . In MPTP models of primate PD along with an increased release of GABA the level of enkephalin in GPe is also increased Betarbet and Greenamyre 2004 . . Neurochemistry of GPe neurons Neurons intrinsic to GPe are of two types those neurons that contain GABA and parvalbumin and project to STN GPi and nigra and those that express GABA and PPE A enkephalin that project to the parvalbu-min containing interneurons of the striatum Bevan et al. 1998 Hoover and Marshall 1999 . Dopamine denervation by either 6-OHDA lesioning of nigra or by administration of D2-antagonists but not D1-antago-nists increases GAD67 mRNA levels in both types of GPe neurons and this increase is reversed by STN lesioning Billings and Marshall 2004 . In PD GABA levels are increased in GPe Kish et al. 1986 . In control brains the GPe neurons do not express mRNA for neurotensin. Dopamine denervation with 6-OHDA however results in the expression of immunoreactivity for neurotensin in neurons of GP in rats Martorana et al. 2003 . The SP dynorphin-containing axons of the direct pathway traverse through GPe but neurons of GPe do not normally express mRNA for SP or for SP receptors. .