Oxygen sensitive chemoreceptors in the first gill arch of the tadpole, Rana catesbeiana

Spike frequency was recorded in the nerve of the isolated superfused first gill arch of the bullfrog larva, Rana catesbeiana and the response to diffe rent superfusate P-O2 was evaluated. In the metamorphic tadpole, spike freq uency increased significantly when the superfusate P-O2 was decreased (mean +/- SEM): 8.5 +/- 1.6 Hz at 650 Torr, 11.7 +/- 1.9 Hz at 140 Torr, 13.3 +/ - 1.8 Hz at 65 Torr, 14.8 +/- 2.4 Hz at 0 Torr (ANOVA, p = 0.0002). The O-2 sensitive chemoreceptor stimulants NaCN and almitrine also increased the s pike frequency. This study demonstrates the presence of O-2 sensitive chemo receptors in the first gill arch of the tadpole.