Effects of metabolic inhibitors and ouabain on static afferent discharges from the isolated frog muscle spindle.

Effects of metabolic inhibitors and ouabain on the rate of afferent discharges from isolated muscle spindle of the bullfrog were examined in vitro to elucidate the mechanism for generating afferent action potentials. Dinitrophenol, NaCN, iodoacetic acid, and ouabain gradually reduced the rate of discharges. These drugs were without direct effect on the nerve axon. The rate of discharges was also reduced by Li+, which is known to be minimally extruded from the interior of cells by an active transport mechanism. The rate of discharges remained approximately 50% in the presence of NaCN or in the absence of oxygen, suggesting that the energy required for the maintenance of the Na+-pump can be supplied to some extent in an anaerobic condition. It appears that the metabolic inhibitors and ouabain reduce the afferent discharges from the frog muscle spindle by affecting the Na+-pump in fibers of nerve terminals.