D(3) dopamine receptors in rat spinal cord: implications for sensory and motor function.

Quantitative autoradiography was used to determine the distribution of D(3) receptors in rat spinal cord and compare it with the distribution of D(1)-like and D(2) (and D(4)) receptors. [(3)H]PD 128907-labeled D(3) sites were observed in roughly 6-fold lower density than [(3)H]spiperone-labeled D(2) (D(4)) sites and 60-fold lower density than [(3)H]SCH 23390-labeled D(1)-like sites. Highest densities of D(3) binding were observed in the superficial layers of the dorsal horn at cervical and lumbar levels followed by the pars centralis and dorsal horn. Lowest densities of D(3) sites were detected in the ventral horn. These observations suggest that spinal D(3) receptors may play a role in sensory and/or motor function or contribute to the pharmacological effects of dopaminergic drugs.