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J. Neurochem. (2011) 116, 966–974. Abstract Dopamine (DA) receptors generate many cellular signals and play various roles in locomotion, motivation, hormone production, and drug abuse. According to the location and expression types of the receptors in the brain, DA signals act in either stimulatory or inhibitory manners. Although DA autoreceptors in the substantia nigra pars compacta are known to regulate firing activity, the exact expression patterns and roles of DA autoreceptor types on the firing activity are highly debated. Therefore, we performed individual correlation studies between firing activity and receptor expression patterns using acutely isolated rat substantia nigra pars compacta DA neurons. When we performed single-cell RT-PCR experiments, D1, D2S, D2L, D3, and D5 receptor mRNA were heterogeneously expressed in the order of D2L > D2S > D3 > D5 > D1. Stimulation of D2 receptors with quinpirole suppressed spontaneous firing similarly among all neurons expressing mRNA solely for D2S, D2L, or D3 receptors. However, quinpirole most strongly suppressed spontaneous firing in the neurons expressing mRNA for both D2 and D3 receptors. These data suggest that D2S, D2L, and D3 receptors are able to equally suppress firing activity, but that D2 and D3 receptors synergistically suppress firing. This diversity in DA autoreceptors could explain the various actions of DA in the brain. |
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