title: Topography and collateralization of dopaminergic projections to primary motor cortex in rats.
abstract: Dopaminergic signaling within the primary motor cortex (M1) is necessary for successful motor skill learning. Dopaminergic neurons projecting to M1 are located in the ventral tegmental area (VTA, nucleus A10) of the midbrain. It is unknown which behavioral correlates are encoded by these neurons. The objective here is to investigate whether VTA-M1 fibers are collaterals of projections to prefrontal cortex (PFC) or nucleus accumbens (NAc) or if they form a distinct pathway. In rats, multiple-site retrograde fluorescent tracers were injected into M1, PFC and the core region of the NAc and VTA sections investigated for concomitant labeling of different tracers. Dopaminergic neurons projecting to M1, PFC and NAc were found in nucleus A10 and to a lesser degree in the medial nucleus A9. Neurons show high target specificity, minimal collateral branching to other than their target area and hardly cross the midline. Whereas PFC- and NAc-projecting neurons are indistinguishably intermingled within the ventral portion of dopaminergic nuclei in middle and caudal midbrain, M1-projecting neurons are only located within the dorsal part of the rostral midbrain. Within M1, the forelimb representation receives sevenfold more dopaminergic projections than the hindlimb representation. This strong rostro-caudal gradient as well as the topographical preference to dorsal structures suggest that projections to M1 emerged late in the development of the dopaminergic systems in and form a functionally distinct system.
authors: Clinical Neurorehabilitation, Department of Neurology, University of Zurich, Frauenklinikstrasse 26, 8091, Zurich, Switzerland.
authors: Jonas A
authors: JA
authors: Hosp
authors: Helen E
authors: HE
authors: Nolan
authors: Andreas R
authors: AR
authors: Luft
mesh_terms: D000818:Animals; D001931:Brain Mapping; D002452:Cell Count; D059290:Dopaminergic Neurons / Q000502:physiology*; D005456:Fluorescent Dyes / Q000378:metabolism; D008297:Male; D009044:Motor Cortex / Q000166:cytology*; D009434:Neural Pathways / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D017557:Ventral Tegmental Area / Q000166:cytology
chemical_list: D005456:Fluorescent Dyes; D014446:Tyrosine 3-Monooxygenase
references: Trends Neurosci. 2007 May;30(5):203-10
references: 17400301
references: Neuroscience. 2009 Mar 17;159(2):692-700
references: 19162136
references: Neuron. 2003 Jun 5;38(5):819-29
references: 12797965
references: J Neurosci. 2004 Jul 21;24(29):6515-20
references: 15269262
references: Annu Rev Neurosci. 2007;30:259-88
references: 17600522
references: PLoS One. 2009 Sep 17;4(9):e7082
references: 19759902
references: J Neurosci Methods. 2000 Nov 15;103(1):23-37
references: 11074093
references: Adv Exp Med Biol. 1986;204:93-118
references: 2947431
references: Trends Neurosci. 1991 Jan;14(1):21-7
references: 1709528
references: Experientia. 1964 Jul 15;20(7):398-9
references: 5856530
references: Int Arch Med. 2010 Oct 06;3:24
references: 20925949
references: PLoS One. 2010 Dec 09;5(12):e15222
references: 21151605
references: J Cogn Neurosci. 1995 Winter;7(1):1-24
references: 23961750
references: J Comp Neurol. 1993 May 15;331(3):297-309
references: 8514911
references: J Neurophysiol. 2002 Dec;88(6):3439-51
references: 12466459
references: Prog Neurobiol. 2000 Nov;62(4):327-51
references: 10856608
references: J Neural Transm. 1976;38(3-4):173-80
references: 956808
references: J Neurosci Methods. 1993 Oct;50(1):45-60
references: 7506340
references: Science. 2000 Oct 20;290(5491):533-6
references: 11039938
references: J Neurosci Methods. 1997 Jun 6;74(1):9-15
references: 9210570
references: J Neurosci. 1996 Jul 15;16(14):4529-35
references: 8699262
references: Neuroscientist. 2005 Oct;11(5):471-83
references: 16151047
references: Neuroscience. 1987 Jun;21(3):807-24
references: 3627435
references: Int J Dev Neurosci. 2009 Aug;27(5):415-21
references: 19446627
references: Behav Brain Res. 2003 Nov 30;146(1-2):3-17
references: 14643455
references: Front Neural Circuits. 2014 Feb 28;8:13
references: 24616667
references: J Cell Biol. 1986 Jun;102(6):2015-22
references: 2423529
references: Science. 1985 May 10;228(4700):752-5
references: 3838821
references: Res Publ Assoc Res Nerv Ment Dis. 1948;27 (1 vol.):210-32
references: 18106857
references: Neuron. 2010 Dec 9;68(5):815-34
references: 21144997
references: Brain Res Bull. 1982 Jul-Dec;9(1-6):321-53
references: 6816390
references: Trends Neurosci. 2007 May;30(5):194-202
references: 17408759
references: Neurosci Lett. 1986 Aug 4;68(3):261-6
references: 2944035
references: Brain Res. 1969 Feb;12(2):321-43
references: 4184997
references: J Neurosci. 2011 Feb 16;31(7):2481-7
references: 21325515
references: J Neurosci Methods. 2002 Jun 30;117(2):167-72
references: 12100982
references: Brain Res. 1987 Aug 18;418(1):27-33
references: 3664272
references: Front Neurol. 2013 Oct 07;4:145
references: 24109472
references: J Neurosci. 1981 Dec;1(12):1361-8
references: 6172572