Differential Reductions in Dopaminergic Innervation of the Motor-Related Areas of the Frontal Lobe in MPTP-Treated Monkeys
Unexpectedly widespread dopaminergic innervation has been recognized in the primate cerebral cortex. The cortical dopaminergic fibers are distributed throughout the frontal-tooccipital extent, with the highest density in the prefrontal and motor-related areas of the frontal lobe.1-10Previous anatomical studies have shown that multiple motor-related areas of the frontal lobe, such as the primary motor cortex (MI), the premotor cortex (PM), and the supplementary motor area (SMA), contain dopaminergic fibers.1–3,7,8,10 The dopaminergic innervation of the motor-related areas is diffuse, involving all cortical layers.3,7,8,10 On the other hand, the cortical dopaminergic fibers as a whole arise from the three catecholaminergic cell groups—A8, A9, and A 10—that are located in the ventral mesencephalon.3 It has been reported that the cells of origin of the mesocortical dopamine projections to the dorsal frontal cortex, including the motor-related areas, are distributed predominantly in the dorsal aspects of the A8–A10 complex.11,12 In primates, the dorsal components of these catecholaminergic cell groups largely correspond to the dorsal part of the retrorubral area, pars gamma (i e, the dorsal tier) of the substantia nigra pars compacta, and the parabrachial pigmented nucleus of the ventral tegmental area, respectively. Given that subpopulations of dopaminergic neurons in such dorsal components may issue axon collaterals to both the frontal cortex and the striatum (for data in the rat, see refs.13,15), it is most likely that at least part of the dopaminergic fibers in the motor-related areas are affected in Parkinson’s disease which is well known to be caused by the extensive loss of dopaminergic nigrostriatal neurons.
KeywordsSucrose Dopamine Tyrosine Serotonin Hydrochloride
Unable to display preview. Download preview PDF.
- 19.German, D.C., Manaye, K.F., Sonsalla, P.K., and Brooks, B.A., 1992, Midbrain dopaminergic cell loss in Parkinson’s disease and MPTP-induced parkinsonism: Sparing of calbindin-D28-containing cellsAnn. N. Y. Acad. Sci.648:42–62.Google Scholar
- 26.Takada, M., Tokuno, H., Nambu, A., and Inase, M., 1998, Corticostriatal projections from the somatic motor areas of the frontal cortex in the macaque monkey: Segregation versus overlap of input zones from the primary motor cortex, the supplementary motor area, and the premotor cortexExp. Brain Res.120:114–128.PubMedCrossRefGoogle Scholar
- 29.Elsworth, J.D., Deutch, A.Y., Redmond, D.E., Jr., Sladek, J.R., Jr., and Roth, R.H., 1990, MPTPinduced parkinsonism: relative changes in dopamine concentration in subregions of substantia nigra, ventral tegmental area and retrorubral field of symptomatic and asymptomatic vervet monkeysBrain Res.513:320–324.PubMedCrossRefGoogle Scholar
- 31.Kastner, A., Hirsch, E.C., Herrero, M.T., Javoy-Agid, F., and Agid, Y., 1993, Immunocytochemical quantification of tyrosine hydroxylase at a cellular level in the mesencephalon of control subjects and patients with Parkinson’s and Alzheimer’s diseaseJ. Neurochem.61:1024–1034.PubMedCrossRefGoogle Scholar
- 36.Jahanshahi, M., Jenkins, I.H., Brown, R.G., Marsden, C.D., Passingham, R.E., Brooks, D.J., 1995, Self-initiated versus externally triggered movements. I. An investigation using measurement of regional cerebral blood flow with PET and.movement-related potentials in normal and Parkinson’s disease subjectsBrain118:913–933.PubMedCrossRefGoogle Scholar