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Title: Adenosine A3 receptor activation inhibits pro-nociceptive N-type Ca2+ currents and cell excitability in dorsal root ganglion neurons.

07:00 EST 24th January 2019 | BioPortfolio

Summary of "Title: Adenosine A3 receptor activation inhibits pro-nociceptive N-type Ca2+ currents and cell excitability in dorsal root ganglion neurons."

Recently studies have focused on the anti-hyperalgesic activity of the A3 adenosine receptor (A3AR) in several chronic pain models, but the cellular and molecular basis of this effect is still unknown. Here, we investigated the expression and functional effects of A3AR on the excitability of small-medium sized, capsaicin-sensitive, dorsal root ganglion (DRG) neurons isolated from 3-4 week-old rats. RT-PCR experiments and immunofluorescence analysis revealed A3AR expression in DRG neurons. Patch-clamp experiments demonstrated that two distinct A3AR agonists, Cl-IB-MECA and the highly selective MRS5980, inhibited Ca-activated K (KCa) currents evoked by a voltage ramp protocol. This effect was dependent on a reduction of Ca influx via N-type voltage-dependent Ca channels (VDCCs) as Cl-IB-MECA-induced inhibition was sensitive to the N-type blocker PD173212 but not to the L-type blocker, lacidipine. The endogenous agonist adenosine also reduced N-type Ca currents, and its effect was inhibited by 56% in the presence of A3AR antagonist MRS1523, demonstrating that the majority of adenosine's effect is mediated by this receptor subtype. Current-clamp recordings demonstrated that neuronal firing of rat DRG neurons was also significantly reduced by A3AR activation in a MRS1523-sensitive but PD173212-insensitive manner. Intracellular Ca measurements confirmed the inhibitory role of A3AR on DRG neuronal firing. We conclude that pain-relieving effects observed upon A3AR activation could be mediated through N-type Ca channel block and action potential inhibition as independent mechanisms in isolated rat DRG neurons. These findings support A3AR-based therapy as a viable approach to alleviate pain in different pathologies.

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Name: Pain
ISSN: 1872-6623
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Medical and Biotech [MESH] Definitions

A stable adenosine A1 and A2 receptor agonist. Experimentally, it inhibits cAMP and cGMP phosphodiesterase activity.

Compounds that selectively bind to and block the activation of ADENOSINE A3 RECEPTORS.

Compounds that selectively bind to and block the activation of ADENOSINE A2 RECEPTORS.

A subclass of adenosine A2 receptors found in LEUKOCYTES, the SPLEEN, the THYMUS and a variety of other tissues. It is generally considered to be a receptor for ADENOSINE that couples to the GS, STIMULATORY G-PROTEIN.

A subclass of adenosine A2 receptors found in the CECUM, the COLON, the BLADDER, and a variety of other tissues. It is generally considered to be a low affinity receptor for ADENOSINE that couples to the GS, STIMULATORY G-PROTEIN.

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