Abstract
Dopamine plays important roles in the development and modulation of
motor control circuits. Here we show that dopamine exerts potent effects
on the central pattern generator circuit controlling locomotory
swimming in post-embryonic Xenopus tadpoles. Dopamine
(0.5–100 μM) reduced fictive swim bout occurrence and caused both
spontaneous and evoked episodes to become shorter, slower and weaker.
The D2-like receptor agonist quinpirole mimicked this repertoire of
inhibitory effects on swimming, whilst the D4 receptor antagonist,
L745,870, had the opposite effects. The dopamine reuptake inhibitor
bupropion potently inhibited fictive swimming, demonstrating that
dopamine constitutes an endogenous modulatory system. Both dopamine and
quinpirole also inhibited swimming in spinalised preparations,
suggesting spinally located dopamine receptors. Dopamine and quinpirole
hyperpolarised identified rhythmically active spinal neurons, increased
rheobase and reduced spike probability both during swimming and in
response to current injection. The hyperpolarisation was TTX-resistant
and was accompanied by decreased input resistance, suggesting that
dopamine opens a K+ channel. The K+ channel
blocker barium chloride (but not TEA, glybenclamide or tertiapin-Q)
significantly occluded the hyperpolarisation. Overall, we show that
endogenously released dopamine acts upon spinally located D2-like
receptors, leading to a rapid inhibitory modulation of swimming via the
opening of a K+ channel.
Original language | English |
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Article number | 35749 |
Journal | Scientific Reports |
Volume | 6 |
DOIs | |
Publication status | Published - 20 Oct 2016 |
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Keith Thomas Sillar
- School of Psychology and Neuroscience - Emeritus Professor
Person: Emeritus Professor