ISSN:
1432-1106
Keywords:
Dopamine
;
Neostriatum-substantia nigra
;
Heteroreceptors
;
D1 receptors
;
SKF-38393
;
SCH-23390
;
Terminal excitability
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The role of dopamine D1 heteroreceptors located on the axon terminals of striatonigral neurons was investigated. Local infusion of the direct acting, specific dopamine D1 agonist, R-SKF 38393, into the substantia nigra terminal field of antidromically identified neostriatal projection neurons decreased the electrical excitability of these axons. This effect was dose-dependent and could be partially reversed by subsequent infusion of the specific D1 antagonist, R-SCH 23390. In contrast, excitability was not affected by the systemic administration of SCH-23390 (0.3 and 0.6 mg/kg, iv), or the non-specific antagonist haloperidol (0.2 mg/kg, iv). Since activation of the D1 heteroreceptors by R-SKF 38393 decreased excitability, the inability of these antagonists to modify excitability indicates that endogenous dopamine does not tonically activate these receptors. Systemic administration of the indirect acting agonist, amphetamine (1.0 and 5.0 mg/kg, iv) also failed to change terminal excitability suggesting that, even when unnaturally high levels of dopamine are released in the substantia nigra, endogenous dopamine does not affect neostriatal axons terminating in the substantia nigra. Thus it is unlikely that endogenous dopamine modulates neostriatal control of the substantia nigra through these presynaptic terminal D1 heteroreceptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00250578
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