The Journal of Neuroscience, May 15, 1999, 19(10):4169-4179
Dopamine Reuptake Inhibition in the Rostral Agranular Insular
Cortex Produces Antinociception
Adam R.
Burkey1,
Earl
Carstens3, and
Luc
Jasmin1, 2
1 Departments of Neurosurgery and 2 Cell
Biology, Georgetown University Medical Center, Washington, DC 20007, and 3 Section of Neurobiology, Physiology and Behavior,
University of California at Davis, Davis, California 95616
We provide evidence for an antinociceptive effect of dopamine in
the rat cerebral cortex that is mediated through descending nociceptive
inhibition of spinal neurons. Injection of the dopamine reuptake
inhibitor GBR-12935 in the rostral agranular insular cortex (RAIC), a
cortical area that receives a dense dopaminergic projection and is
involved in descending antinociception (Burkey et al., 1996), resulted
in dose-dependent inhibition of formalin-induced nociceptive behavior,
without any alteration of motor function. Injection of the dopamine
reuptake inhibitor in the surrounding cortical areas had no effect on
nociceptive behaviors. GBR-12935 also produced a reduction in noxious
stimulus-induced c-fos expression in nociceptive areas
of the spinal dorsal horn, suggesting that dopamine in the RAIC acts in
part through descending antinociception. Electrophysiological recording
from single wide dynamic range-type spinal dorsal horn neurons
confirmed the descending nociceptive inhibitory effect. GBR-12935 in
the RAIC significantly reduced neuronal responses evoked by noxious
thermal stimulation of the skin, an effect that was reversed by local
administration of the selective D1 receptor antagonist SCH-23390.
Finally, administration of SCH-23390 alone in the RAIC decreased paw
withdrawal latencies from noxious heat, suggesting that dopamine acts
tonically in the cortex to inhibit nociception.
Key words:
pain; cerebral cortex; descending inhibition; D1
receptor; dopamine reuptake inhibitor; GBR-12935; dopamine antagonist; SCH-23390
Copyright © 1999 Society for Neuroscience 0270-6474/99/19104169-11$05.00/0