The effects of melatonin on D(2) dopaminergic function: Implications for motor behavior and gene expression
The present experiments were conducted to elucidate the relationship between melatonin and the D2 dopaminergic system in context of extrapyramidal motor behavior and striatal gene expression in both the light and dark phases. Light phase melatonin treatment in rats significantly reduced D2 antagonist-induced hypokinesia. Paradoxically, dark phase melatonin treatment significantly increased D2 antagonist-induced hypokinesia. Additionally, melatonin treatment in the light phase significantly decreased D2 agonist induced-stereotypies with an especially strong effect on the stereotypy licking. Further, a strong diurnal effect in the D 2 system was uncovered. D2 antagonist activation induced robust extrapyramidal effects only during the light phase. The D2 agonist showed its strongest effects during the dark phase. Furthermore, it was shown for the first time that melatonin exerts strong diurnal effects on striatal gene expression whereby melatonin upregulated genes during the light phase and down regulated genes in the dark phase. The significance of these findings in the context of melatonin's effect on extrapyramidal function both in humans and animals is discussed.
Sumaya, Isabel Cecilia, "The effects of melatonin on D(2) dopaminergic function: Implications for motor behavior and gene expression" (2001). ETD Collection for University of Texas, El Paso. AAI3035103.