open access

https://hdl.handle.net/2115/52711

Inhibitory effects of dopamine on spinal synaptic transmission via dopamine D1-like receptors in neonatal rats

英語

reflex potentials

2012-05

Blackwell Publishing

British Journal of Pharmacology

166(2)

788-800

BACKGROUND AND PURPOSE: Dopamine released from the endings of descending dopaminergic fibre in the spinal cord is suggested to be involved in modulating functions such as locomotion and nociception. Here, we examined the effects of dopamine on spinal synaptic transmissions in rats. EXPERIMENTAL APPROACH: Spinal reflex potentials, monosynaptic reflex potential (MSR) and slow ventral root potential (sVRP), were measured in the isolated spinal cord of the neonatal rat. Dopamine release was measured by using HPLC. KEY RESULTS: Dopamine at lower concentrations (< 1 μM) depressed sVRP, which is C fibre-evoked polysynaptic response and believed to reflect nociceptive transmission. At higher concentrations (> 1 μM), in addition to a potent sVRP depression, dopamine depolarized baseline potential and slightly depressed MSR. Depression of sVRP by dopamine was partially reversed by dopamine D1-like but not by D2-like receptor antagonists. SKF83959 and SKF81297, D1-like receptor agonists, and methamphetamine, an endogenous dopamine releaser, also caused the inhibition of sVRP. Methamphetamine also depressed MSR, which was inhibited by ketanserin, a 5-HT_[2A/2C] receptor antagonist. Methamphetamine induced the release of dopamine and 5-HT from spinal cords, indicating that the release of endogenous dopamine and 5-HT depresses sVRP and MSR respectively. CONCLUSION AND IMPLICATIONS: These results suggest that dopamine at lower concentrations preferentially inhibits sVRP, which is mediated via D1-like and unidentified receptors. The dopamine-evoked depression is involved in modulating the spinal functions by the descending dopaminergic pathways.

学術雑誌論文

Accepted Manuscript

The definitive version is available at http://onlinelibrary.wiley.com

0007-1188