A and B, original traces of three distinct inward currents evoked by pH 6.0 in DRG neurones, and the different percentages of the three types of currents responsive to pH 6.0 and 4.0 in DRG neurones. C and D, original traces and average data show that a greater peak amplitude of inward currents responsive to low pH was seen in the neurones innervating white muscle than in those innervating red muscle. pH 4.0 induced greater amplitude of inward currents in the neurones innervating white and red muscle as compared with pH 6.0. *P < 0.05, versus pH 6.0. †P < 0.05, versus red muscle.