Invited Symposium: What Can Genetic Models Tell Us About Attention-Deficit Hyperactivity Disorder (ADHD)?
Ashby, CR Jr. (Department of Pharmaceutical Health Sciences, St. John's University, USA)
The mesotelencephalic dopamine (DA) system is heterogeneous with respect to nuclei, terminal loci, DA receptor subtypes, electrophysiological characteristics and response patterns, and neuropharmacological response to a range of agents. The majority of mesocortical and mesolimbic DA neurons originate in the ventral tegmental area. In contrast, the nigrostriatal DA neurons originate in substantia nigra pars compacta. DA neurons originating from the retrorubal field appear to innervate primarily subcortical limbic and neostriatal terminal loci. The nigrostriatal terminal loci appear to have relatively low densities of D3 and D4 receptors, compared to mesolimbic and mesocortical loci. The D1, D2, and D5 receptors appear more homogeneously distributed. Electrophysiologically, nigrostriatal DA neurons tend to show more regularity in firing pattern (fewer bursting events), and a lower basal firing rate than mesolimbic or mesocortical neurons. Neuropharmacologically, mesocortical DA neurons are significantly less responsive to intravenous D-amphetamine, (+)-apomorphine, and chronic antipsychotic drug treatment. Mesocortical DA neurons are also relatively insensitive to iontophoretically-applied DA, a finding congruent with the reported relative lack of somato-dendritic autoreceptors in the mesocortical component. Neurochemically, mesoaccumbens DA neurons appear more sensitive to the systemic administration of drugs with addictive liability.
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|Gardner, EL; Ashby, Jr.; (1998). Heterogeneity of the Mesotelencephalic Fibers: Physiology and Pharmacology. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/sadile/gardner0358/index.html|
|© 1998 Author(s) Hold Copyright|