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.
Anden N.-E., Dahlstrom A., Fuxe K., & Larsson K. ( 1966). "Functional role of the- nigro-neostriatal dopamine neurons". Acta Pharmacologica et Toxicologica, 24,263-274.
Camp L. L., & Rudy J. W. ( 1987). "Behavioral activation in infant rats: Pharmacological evidence for dopaminergic mediation". Psychobiology, 15,318-328.
Cheramy A., Leviel V., & Glowinski J. ( 1981). "Dendritic release of dopamine in the substantia nigra". Nature (London), 289,537-542.
Das G. D., & Altman J. ( 1970). "Postnatal neurogenesis in the caudate nucleus and nucleus accumbens septi in the rat". Brain Research, 21,122-127.
Fishell G., & van der D Kooy. ( 1987). "Pattern formation in the striatum: Developmental changes in the distribution of striatonigral neurons". Journal of Neuroscience, 7,1969-1978.
Fishell G., & van der D Kooy. ( 1989). "Pattern formation in the striatum: Developmental changes in the distribution of striatonigral projections". Developmental Brain Research, 45, 239-255.
Garcia-Rill E. ( 1986). "The basal ganglia and the locomotor regions". Brain Research Reviews, 11,47-63.
Garcia-Rill E., Kinjo N., Atsuta Y., Ishikawa Y., Webber M., & Skinner R. D. ( 1990). "Posterior midbrain-induced locomotion". Brain Research Bulletin, 24,499-508.
Gerfen C. R., Staines W. A., Arbuthnott G. W., & Fibiger H. C. ( 1982). "Crossed connections of the substantia nigra in the rat". Journal of Comparative Neurology, 207,283-303.