RT Journal Article
SR Electronic
T1 The Role of Dopamine Receptors in Regulating the Size of Axonal Arbors
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 5147
OP 5157
DO 10.1523/JNEUROSCI.21-14-05147.2001
VO 21
IS 14
A1 C. L. Parish
A1 D. I. Finkelstein
A1 J. Drago
A1 E. Borrelli
A1 M. K. Horne
YR 2001
UL http://www.jneurosci.org/content/21/14/5147.abstract
AB Factors that regulate terminal arbor size of substantia nigra pars compacta (SNpc) neurons during development and after injury are not well understood. This study examined the role of dopamine receptors in regulating arbor size. Terminal arbors were examined in mice with targeted deletion of the D1 or D2 dopamine receptor [D1(−/−) and D2(−/−) mice, respectively]. Terminal trees were also examined after treatment with receptor blockers and after partial SNpc lesions. Immunohistochemistry was performed, and the number of SNpc neurons and dopaminergic terminals in the striatum was estimated. The number of dopaminergic SNpc neurons were reduced in D1(−/−) and D2(−/−) mice. Density of dopaminergic terminals was unchanged in D1(−/−) mice and increased in D2 (−/−) mice. Steady-state striatal DA and DOPAC levels revealed that dopamine activity was enhanced in D2(−/−) mice but reduced in D1(−/−) mice.Two months after partial SNpc lesions, striatal terminal density was normal in both wild-type and D1(−/−) mice but reduced in D2(−/−) mice. Administration of DA receptor antagonists resulted in larger terminal arbors in D1(−/−) and wild-type mice, whereas D2(−/−) mice showed no change in terminal density.Functional blockade of the D2R during development or in the adult brain results in increased axonal sprouting. Partial SNpc lesions resulted in compensatory sprouting, only in mice with functional D2R. These results suggest that individual dopaminergic axons in D2(−/−) mice have reached maximal arbor size. We conclude that the D2 receptor may play a role in modulating the extent of the terminal arbor of SNpc neurons.