In the research reported here, the functional maturation of dopamine systems has been studied by measuring the effects of dopamine agonists on simple motor behaviors in developing rat pups. Cannulation of dopamine unilaterally into the neonatal striaturn resulted in contralateral postural deviation, whereas quinpirole injected bilaterally led to agedependent changes in locomotion at 10-30 days of age. Thus, dopamine receptors in the striatum can modulate motor behaviors quite early in ontogeny, although the adult pattern of biphasic locomotor effects of quinpirole appears only between 20-30 days of age. However, the indirect dopamine agonist L-DOPA activates a particular kind of locomotion, air-stepping, throughout ontogeny in decerebrate as well as intact rats. These locomotor effects of L-DOPA are thus independent of its actions on the forebrain and must take place in the brainstem. It is thus possible that in parkinsonian patients, at least some of the therapeutic effects of L-DOPA or its metabolites may also take place at the level of the brainstem.
The research described here was supported by NS22850 to D. J. Stehouwer and C. Van Hartesveldt, and by a Whitehall Foundation grant to C. Van Hartesveldt.
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Publication information: Book title: Neurobehavioral Plasticity:Learning, Development, and Response to Brain Insults. Contributors: Norman E. Spear - Editor, Linda P. Spear - Editor, Michael L. Woodruff - Editor. Publisher: Lawrence Erlbaum Associates. Place of publication: Hillsdale, NJ. Publication year: 1995. Page number: 345.
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