Capsaicin and N-Arachidonoyl-dopamine (NADA) Decrease Tension by Activating Both Cannabinoid and Vanilloid Receptors in Fast Skeletal Muscle Fibers of the Frog

Abstract

Previous studies have indicated that vanilloid receptor (VR1) mRNA is expressed in muscle fibers. In this study, we evaluated the functional effects of VR1 activation. We measured caffeine-induced contractions in bundles of the extensor digitorum longus muscle of Rana pipiens. Isometric tension measurements showed that two VR1 agonists, capsaicin (CAP) and N-arachidonoyl-dopamine (NADA), reduced muscle peak tension to 57 ± 4 % and 71 ± 3% of control, respectively. The effect of CAP was partially blocked by a VR1 blocker, capsazepine (CPZ), but the effect of NADA was not changed by CPZ. Because NADA is able to act on cannabinoid receptors, which are also present in muscle fibers, we tested the cannabinoid antagonist AM281. We found that AM281 antagonized both CAP and NADA effects. AM281 alone reduced peak tension to 80 ± 6 % of control. With both antagonists, the CAP effect was completely blocked, and the NADA effect was partially blocked. These results provide pharmacological evidence of the functional presence of the VR1 receptor in fast skeletal muscle fibers of the frog and suggest that capsaicin and NADA reduce tension by activating both cannabinoid and vanilloid receptors.

Effects of Chronic Administration of Capsaicin on Biomarkers of Kidney Injury in Male Wistar Rats with Experimental Diabetes

“…Additionally, the sexes have shown different predispositions to developing kidney injury due to diabetes [37]. Moreover, as mentioned above, previous studies have provided evidence that CAPS was capable of stimulating receptors other than TRPV1, like CB1 receptors [8], which were reported to be overexpressed in DN kidneys. Therefore, in future studies, we plan to use both sexes of rats when examining the CAPS effect together with an antagonist of the CB1 receptor.…”

“…CAPS treatment also reduced the expression of inflammation markers and oxidative stress [7]. However, it was recently reported that CAPS could also activate cannabinoid brain type 1 (CB1) receptors [8]. CB1 receptors were reported to be expressed in podocytes [9].…”

The Contractile Phenotype of Skeletal Muscle in TRPV1 Knockout Mice Is Gender-Specific and Exercise-Dependent

“…The literature on the impact of the pharmacological modulation of TRPV1 on muscle function is barely more abundant. Only one study revealed that pharmacological activation of TRPV1 by capsaicin decreases the tension of fast muscles in frogs [ 47 ].…”

Molecular networks underlying cannabinoid signaling in skeletal muscle plasticity

“…Oláh et al (2016) found that activation of the CB 1 ‐Gα protein pathway induces muscle fatigability that can be (partly) explained by a decrease in Ca 2+ sensitivity and a lower RyR‐mediated Ca 2+ release (Oláh et al, 2016). Accordingly, CB 1 agonism reduced the maximum tension of contractions in frog muscle fibers, induced by caffeine, which is known to induce Ca 2+ release from the sarcoplasmic reticulum (Huerta et al, 2009; M. G. Klein et al, 1990; Trujillo et al, 2015). Besides Ca 2+ , also Na + can be modulated by cannabinoid signaling to orchestrate muscle excitability.…”