Ito et al., 2020 - Identification of the hypertension drug niflumic acid as a glycine receptor inhibitor. Scientific Reports   10:13999 Full text @ Sci. Rep.

Figure 1

Bath application of strychnine, picrotoxin, nifedipine or niflumic acid to zebrafish embryos at 48 hpf caused abnormal touch response touch. (a) A superimposed image of 100 Hz movie frames. A control wild-type embryo (1% DMSO) responded to tactile stimulation and showed swimming by side-to-side trunk contractions. (b) Strychnine-treated embryos responded to touch by bilateral muscle contractions that resulted in shortening of the body along anterior–posterior axis. (c) Picrotoxin-treated embryos exhibited similar shrinkage of the body. (d) Nifedipine-treated embryos showed similar abnormal touch response. (e) Niflumic acid-treated embryos also responded to touch by bilateral muscle contractions.

Figure 2

Heteromeric GlyR decreased glycine sensitivity compared with homomeric GlyR. (a) A trace of two-electrode voltage-clamp recording from oocyte injected with five femtomoles of zGlyRα1 cRNAs exposed to serial application of glycine of increasing amounts. (b) Cumulative concentration–response relationship of glycine-evoked currents. The amplitude of glycine-evoked currents was normalized to the maximally-evoked current as 100% for each oocyte (n = 10). Values here and elsewhere represent mean ± SEM.

Figure 3

Drug-mediated inhibition of homomeric and heteromeric zebrafish GlyRs. (a) A recording from a zGlyRα1-injected oocyte exposed to 200 µM glycine with increasing amounts of niflumic acid. (b) Cumulative concentration-dependent inhibition of GlyRα1 current by strychnine, picrotoxin, nifedipine and niflumic acid (n = 10 each). (c) A recording from an oocyte, which were injected with zGlyRα1 and zGlyRβb and exposed to 200 µM glycine with increasing amounts of niflumic acid. (d) Cumulative concentration-curves of strychnine, picrotoxin, nifedipine and niflumic acid-mediated inhibition of α1/βb heteromeric zebrafish GlyRs (n = 10 each).

Figure 4

Drug-mediated inhibition of homomeric and heteromeric human GlyRs. (a) A recording from a hGlyRα1-injected oocyte exposed to 200 µM glycine with increasing amounts of niflumic acid. (b) Cumulative concentration-dependent inhibition of GlyRα1 current by strychnine, picrotoxin, nifedipine and niflumic acid (n = 10 each). (c) A recording from an oocyte, which were injected with hGlyRα1 and hGlyRβ and exposed to 200 µM glycine and increasing amounts of niflumic acid. (d) Cumulative concentration-curves of strychnine, picrotoxin, nifedipine and niflumic acid-mediated inhibition of α1/β heteromeric human GlyRs (n = 10 each).

Acknowledgments:
ZFIN wishes to thank the journal Scientific Reports for permission to reproduce figures from this article. Please note that this material may be protected by copyright. Full text @ Sci. Rep.